Three marks, one prior question
Before choosing between a period, a semicolon and a colon, answer the same question that governs every boundary item: what stands on each side?
- Period. Independent clause on the left, independent clause on the right.
- Semicolon. Independent clause on the left, independent clause on the right — the same demand, word for word.
- Colon. Independent clause on the left; on the right, anything at all: another clause, a noun phrase, a list, a single word.
The colon is the only one of the three that is generous about its right side and strict about its left. The period and the semicolon are strict about both sides and are strict in exactly the same way.
Ba dấu này chia làm hai nhóm chứ không phải ba. Dấu chấm và dấu chấm phẩy yêu cầu hai bên đều là mệnh đề độc lập — yêu cầu giống nhau từng chữ. Dấu hai chấm khác hẳn: bên trái bắt buộc là mệnh đề độc lập, còn bên phải muốn là gì cũng được, kể cả một từ. Nhớ đúng bảng này là đã xử được phần lớn câu hỏi của nhóm.
Radiocarbon dating placed the textile in the twelfth centurythe weaving technique was not documented in the region until three hundred years later.
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Both sides are independent clauses. (A) is a comma splice. (C) would announce that the second clause delivers what the first promises, but the first promises nothing — it simply reports a date, and the second reports a conflicting fact. (D) puts a coordinating conjunction between two clauses without the required comma. The semicolon joins the two statements and leaves the tension between them for the reader. Answer (B).
The period and the semicolon are the same mark
Grammatically there is no difference between them. That fact is worth points, because a test item can have only one correct answer.
Elimination rule. If a period and a semicolon both appear among the four choices, and the material on both sides would be identical either way, then neither can be the answer. Cross both out and decide between the remaining two.
The tomb had been sealed for more than two thousand yearsthe pigments on its walls remain vivid.
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(A) and (B) would produce sentences that are punctuated differently but parsed identically, so they stand or fall together; since only one choice can be correct, both fall. That leaves (C) and (D). (C) is a comma splice. (D) uses a comma plus the coordinating conjunction yet, which is legal and which also states the contrast the sentence is built on. Answer (D).
Đừng dừng lại ở chỗ “dấu chấm phẩy nối được hai mệnh đề độc lập, vậy chọn nó”. Nếu dấu chấm cũng có mặt trong bốn phương án và hai bên chỗ trống không đổi, thì hai phương án đó tương đương tuyệt đối — mà đề chỉ có một đáp án. Cả hai cùng sai. Đáp án nằm ở hai phương án còn lại.
The colon depends entirely on what stands before it
Everything to the left of a colon must be able to stand as a sentence. The most productive trap in this domain puts the colon immediately after a verb or a preposition, where the sentence is still waiting for its complement.
The three instruments carried by the probe werea magnetometer, a dust detector, and a wide-angle camera.
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The three instruments carried by the probe were is not a sentence; the linking verb were has not received its complement yet. A colon may not follow it, and neither may a semicolon or a comma, both of which would cut the verb off from what completes it. Nothing belongs in the slot. Answer (B).
The sculptor worked almost exclusively inmarble, bronze, and fired clay.
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In is a preposition still waiting for its object. A colon after a preposition is always wrong, however natural the pause sounds, and a comma or semicolon between a preposition and its object is no better. Answer (C).
Hai chỗ dấu hai chấm bị cấm tuyệt đối: ngay sau động từ (were, included, are) và ngay sau giới từ (in, of, from, with). Cách kiểm nhanh là che phần bên phải đi rồi đọc phần bên trái — nếu nó còn đang treo, chưa thành câu, thì mọi dấu đều sai chứ không riêng dấu hai chấm.
What a colon may introduce
Once the left side is a full clause, the right side is free: a list, an appositive noun phrase, a single word, or another independent clause.
The survey turned up a single anomalya buried stone wall running perpendicular to every other structure on the site.
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A buried stone wall running perpendicular… has no finite verb, so it is a noun phrase. A semicolon or a period would leave it stranded as a fragment, which removes (A) and (D). (B) attaches it as a second object of turned up with an ungrammatical comma before and, and it changes the meaning to two separate finds. The colon delivers the anomaly the first clause announced. Answer (C).
The ice core told a consistent storya rise in atmospheric carbon dioxide before every warming episode in the record.
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The same shape again, with a longer noun phrase on the right. The left side is a complete sentence and the right side has no finite verb, so (A) and (B) create fragments and (D) yokes a rise to a consistent story as a second object of told, which is nonsense. Answer (C).
A colon does not require a list. One word is enough: Only one material survives the firing: cobalt.
Semicolons as super-commas
A semicolon has a second job. When the items of a list already contain commas, the items are separated by semicolons instead, including before the final and.
Delegates arrived from Uppsala, SwedenKyoto, Japanand Valparaiso, Chile.
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Each item is a city followed by a country, so each already carries an internal comma. Using commas as separators as well, in (B), produces six apparent items instead of three. The separators must be raised to semicolons, and they must be raised consistently, which removes the mixed pairs (C) and (D). Answer (A).
Dấu chấm phẩy trong danh sách không phải là ngoại lệ kỳ quặc — nó là cách duy nhất để phân biệt ranh giới giữa các mục với dấu phẩy nằm bên trong từng mục. Đã nâng lên dấu chấm phẩy thì phải nâng ở mọi ranh giới giữa các mục, kể cả ranh giới trước and cuối cùng. Trộn hai loại là sai.
When the left side is not a clause at all
The hardest items in this group hide a dependent clause on the left, where the eye expects a sentence because the material is long.
Because the sediment cores had been stored in unrefrigerated crates for a decadethe organic fraction was useless for dating.
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Because… subordinates everything up to decade, so the left side is a dependent clause no matter how long it runs. A colon and a semicolon both require an independent clause on the left, so (B) and (C) are out; leaving the slot empty runs the introductory clause into the main clause. Answer (A).
Bioluminescence has evolved independently in more than forty lineagesthe underlying chemistry, however, is remarkably uniform.
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Both sides are independent; however here sits inside the second clause as a parenthetical and does no joining work. (A) splices. (C) adds but on top of however, stacking two contrastive connectives, and omits the comma that but would need. (D) promises delivery that the second clause does not supply — it contradicts rather than explains. Answer (B).
Một cụm dài không tự thành mệnh đề độc lập. Trước khi chọn dấu chấm phẩy hay dấu hai chấm, hãy đọc riêng phần bên trái chỗ trống và tự hỏi “chấm ở đây được không?”. Nếu câu trả lời là không thì hai dấu đó bị loại ngay, không cần cân nhắc nghĩa.