Question 113·Medium·Form, Structure, and Sense
Built on a foundation of innovative engineering, _____ dramatically reduced travel times across the rugged Andes Mountains.
Which choice completes the text so that it conforms to the conventions of Standard English?
For modifier-placement questions, first identify what the introductory phrase logically describes (here, the thing that was built). Then scan each option to see what noun comes immediately after that phrase; eliminate any that make the modifier describe the wrong noun (often “people” instead of an object). Finally, check that the remaining choice forms a clear, grammatical main clause with minimal clutter—subject right after the comma, then verb, then any extra descriptive phrases set off correctly by commas.
Hints
Match the modifier to the right noun
Focus on the opening phrase: “Built on a foundation of innovative engineering.” What specific thing in the sentence was actually built that way? Make sure that thing appears immediately after the comma.
Check for dangling modifiers
Ask yourself: In each option, does the phrase after the blank accidentally describe engineers instead of the structure itself? If so, that option creates a dangling modifier and should be eliminated.
Look for a clear, simple main clause
When you insert the choice, ignore the extra descriptive phrase about the year and check that you still have a clean main clause: [subject] + [verb] + “dramatically reduced travel times …” without extra, awkward add-ons like “and it.”
Step-by-step Explanation
Identify what the opening phrase is describing
The sentence begins with the participial phrase “Built on a foundation of innovative engineering,” followed by a comma. Whatever comes immediately after this comma must be the thing that was built on a foundation of innovative engineering.
Ask: What was built on a foundation of innovative engineering? It’s the railway, not the engineers.
Check each answer’s subject right after the comma
Plug each option into the blank and see what noun or subject comes right after the opening phrase.
- A) “Built on a foundation of innovative engineering, completed in 1910, engineers built the Trans-Andean Railway, which …” → This makes it sound like engineers were built on a foundation, which is wrong.
- C) “Built on a foundation of innovative engineering, engineers completed the Trans-Andean Railway in 1910 and it …” → Again, this says the engineers were built on a foundation.
- D) “Built on a foundation of innovative engineering, in 1910, building the Trans-Andean Railway, engineers dramatically reduced …” → Still suggests engineers were built.
Only the correct choice will place the railway (not engineers) as the thing described by the opening phrase.
Check for complete, clear main clause and modifier use
The completed sentence needs a clear main clause (subject + verb) and correctly placed extra information.
We want:
- Subject: the thing built on a foundation of innovative engineering (the railway)
- Verb: what that thing did (dramatically reduced travel times)
- Extra info like the completion year should be set off with commas and not break the sentence.
Options A, C, and D either:
- Create dangling modifiers (describing the wrong noun), or
- Create clumsy or incorrect clauses (extra “and it,” too many comma phrases, etc.).
Choose the option that keeps the sentence grammatical and logical
Now plug in the remaining logical structure:
“Built on a foundation of innovative engineering, the Trans-Andean Railway, completed in 1910, dramatically reduced travel times across the rugged Andes Mountains.”
This version correctly:
- Makes the Trans-Andean Railway the subject being described by “Built on a foundation of innovative engineering,” and
- Uses “completed in 1910” as a nonessential phrase set off by commas.
So the correct answer is “the Trans-Andean Railway, completed in 1910,” (choice B).