Select the most appropriate option to substitute the highlighted segment in the given sentence.
The secretary to my boss is very efficient as he not only gives him the required information and also handles correspondence independently.

Correct option is B

The correct substitution of the highlighted words is (b) but also handles.

Explanation:
The correlative conjunction pair "not only... but also" should always be used in tandem to ensure parallel structure in the sentence.
“Not only... and also” is incorrect as it breaks the grammatical balance.

Corrected sentence:
The secretary to my boss is very efficient as he not only gives him the required information but also handles correspondence independently.

Grammatical rule used:
Correlative conjunctions like not only... but also, either... or, neither... nor must maintain symmetry and balance in structure.

Example:
She not only sings but also plays the piano.

Information Booster:
Avoid mixing correlative pairs.
Ensure the verb or phrase following both parts is parallel in form.