Question

Fill in the blank with the most appropriate word.
A: He is a doctor. He looks very young.
B: Yes. He doesn't look old enough _____ a doctor.

• A. being
• B. be
• C. been
• D. to be

Answer 1

Answer: (D)

to be

The infinitive verb is a verb with the word 'to' in front of it. This verb is always just a verb. There is no - ed, no - ing, no - s at the end of the verb. To-infinitive is used with adverb. 'Enough' is an adverb. Option A is used with passive voice while the sentence is in active voice. Options B and C don't make the sentence grammatically correct. Thus, options A, B and C are wrong according to the rule. The correct option is D since 'to' is in front of the verb 'be' and is used with adverb 'enough'.