Select the option that will improve the highlighted part of the given sentence. In case no improvement is needed, select 'No improvement required'.
I don't know why he is such secretly.

Correct option is D

The correct substitution of the highlighted words is is so secretive.
Explanation:
· The word "such" is incorrectly used before an adverb ( secretly).
· The correct structure should use "so" before an adjective ( secretive).
· "Secretly" is an adverb (describes an action), but we need "secretive", an adjective, to describe "he" (a noun).
Grammatical rule used:
Adjectives describe nouns (he → secretive), while adverbs describe verbs (act secretly).
Example:
· Incorrect: He is such secretly about his plans. ❌
· Correct: He is so secretive about his plans. ✅