Question 39·Hard·Form, Structure, and Sense
Unique mechanical durability, negligible energy loss over long distances, and compatibility with existing fiber infrastructure ______ superconducting power cables an attractive option for urban electrical grids, motivating utilities to fund large-scale pilot projects.
Which choice completes the text so that it conforms to the conventions of Standard English?
For subject–verb agreement questions, first isolate the subject by ignoring descriptive phrases and prepositional phrases. Decide if the subject is singular or plural, especially when it’s a list joined by "and." Then check each answer choice to see which verb form both (1) matches the subject in number and tense and (2) fits the sentence structure as a complete, grammatical clause. Quickly rule out participle or phrase forms (like "by doing," "having done") when the blank clearly needs a main verb.
Hints
Find the subject before the blank
Read from the beginning up to the blank and decide what the main subject of the sentence is. Is it one thing or a list of several things?
Decide what kind of word the blank needs
Look at the structure around the blank: something "_____ superconducting power cables an attractive option." Think about whether you need a main verb or a phrase starting with a preposition or participle.
Match verb form to the subject
Once you know whether the subject is singular or plural, eliminate any answer choices whose verb form does not agree with that subject in number.
Step-by-step Explanation
Identify what role the blank plays in the sentence
Look at the words immediately around the blank: "...infrastructure ______ superconducting power cables an attractive option..."
The blank comes right after the long subject list and right before the object phrase "superconducting power cables."
So the blank must be filled with the main verb that tells what the subject does to superconducting power cables (what they do to make them an attractive option).
Determine the subject and its number (singular vs. plural)
The subject of the sentence is a list of three items:
- Unique mechanical durability
- negligible energy loss over long distances
- compatibility with existing fiber infrastructure
These three items are joined with "and", which creates a compound subject. A compound subject joined by "and" is generally plural, so it needs a plural verb form.
So we are looking for a verb form in the answers that correctly agrees with a plural subject and can serve as the main verb of the sentence.
Test each choice for verb agreement and sentence structure
Now check each option with the subject and rest of the sentence:
"Unique mechanical durability, negligible energy loss over long distances, and compatibility with existing fiber infrastructure ____ superconducting power cables an attractive option for urban electrical grids..."
- "makes" is singular, but our subject is plural, so this creates a subject–verb agreement error.
- "by making" introduces a phrase ("by making...") instead of providing the main verb; the sentence would lack a proper main verb and become ungrammatical.
- "having made" is a participle (used in perfect tenses or phrases like "having made"), not a simple main verb; it does not fit as the main verb of this clause.
- "make" is plural and can act as the main verb: the three qualities make superconducting power cables an attractive option.
The choice that correctly matches the plural subject and completes the sentence as a clear, grammatical statement is "make."