Choose the option that best replaces the underlined phrase:

"Happy is the man who acquired the habit of reading when he is young."

The clauses 'happy is the man' and 'when he is young' are both in the simple present tense. The underlined phrase, 'who acquired', should, therefore, also be in the simple present tense. The verb 'acquired' becomes 'acquires' in simple present tense (and not 'acquire' which would allude to plural 'men' and not 'man') and therefore, the correct sentence would be:

"Happy is the man who acquires the habit of reading when he is young."

The correct answer is, therefore, option A.