Question

Choose the correct verb to complete the sentence: 'The number of students who have opted for the elective course ___ increased significantly this year.'

• A. have
• B. having
• C. has
• D. were

Hint:

Check whether the sentence begins with "The number of" or "A number of", since these two near-identical phrases take opposite verb forms.

Answer 1

The Correct Option is C

Step 1: Use the substitution test that distinguishes "the number of" from "a number of": mentally replace the subject phrase with just "amount" or "quantity" (singular ideas) versus "several" (a plural idea) to see which fits better.
Step 2: "The number of students" refers to one single figure, a count or amount, so it behaves as a singular subject, similar to saying "The amount has increased." In contrast, "A number of students have opted..." would describe several individual students and take a plural verb, but that is not the phrasing used here.
Step 3: Since the sentence uses the definite article "The number of", the grammatical subject is "the number" itself, not "students", and it must take the singular verb "has".
Step 4: Eliminate the alternatives: "have" and "were" are plural forms that would only suit "A number of students"; "having" is a non-finite participle that cannot stand as the main verb of an independent clause.
Correct option: (3) has.