Question 102·Hard·Boundaries
Advocates of high-speed rail often highlight its environmental benefits; _____ contend that construction emissions can offset any long-term gains.
Which choice completes the text so that it conforms to the conventions of Standard English?
For punctuation and sentence-boundary questions, first identify how many complete clauses (subject + verb) you have and notice any existing punctuation like semicolons or periods. Decide whether the blank is between clauses (where you might need a semicolon, period, or comma + conjunction) or inside a clause (where you might need commas around interrupters like however, therefore, or for example). Then test each option by reading the sentence and checking: 1) Do I still have complete clauses where needed? 2) Am I avoiding double punctuation (like two semicolons)? 3) Are transition words correctly set off with commas when they interrupt the sentence?
Hints
Look at the clauses around the blank
Identify the subject and verb before and after the blank. Ask yourself: Is the missing punctuation joining two sentences, or is it sitting inside one sentence between a subject and its verb?
Focus on how 'however' is used
In this sentence, 'however' comes between the subject and the verb that follows. Think about how interrupters or transition words inside a clause are usually punctuated.
Use the existing semicolon as a clue
There is already a semicolon before the blank. Do you need another semicolon immediately after the subject, or do you mainly need commas to separate the interrupter from the rest of the clause?
Compare the comma patterns
Compare where the commas fall in each choice. Which pattern cleanly sets off the transition word in the middle of the second clause without breaking the flow between the subject and the verb?
Step-by-step Explanation
Understand the sentence structure
Read the full sentence:
"Advocates of high-speed rail often highlight its environmental benefits; _____ contend that construction emissions can offset any long-term gains."
There are two complete ideas (independent clauses):
- Clause 1: Advocates ... highlight its environmental benefits
- Clause 2: _____ contend that construction emissions can offset any long-term gains
The semicolon already correctly connects these two clauses. The blank sits inside the second clause, between the subject and the verb (critics contend).
Identify the role of 'however'
The word that appears in every answer choice is 'however'. Here, 'however' is a transition that contrasts what critics think with what advocates think.
Inside a clause, words like 'however', used as interrupters between the subject and the verb, are usually set off with commas on both sides (they act like a parenthetical word). The punctuation around 'however' must reflect that.
Check how each option affects the punctuation
We must:
- Keep the existing semicolon that joins the two independent clauses.
- Avoid adding an unnecessary second semicolon inside the second clause.
- Correctly set off 'however' within the second clause so that the subject–verb relationship (critics contend) remains clear.
Look for the choice that places commas around 'however' (since it interrupts the subject and verb) without inserting another semicolon.
Choose the option that fits standard punctuation rules
The only option that correctly punctuates the interrupter and preserves the sentence structure is "critics, however,".
The sentence becomes:
"Advocates of high-speed rail often highlight its environmental benefits; critics, however, contend that construction emissions can offset any long-term gains."