He is . . . . . . union leader.

A. a

B. an

C. the

D. article not required

Answer: Option C

Solution(By Examveda Team)

"The" is a definite article which is used before a noun that is fixed, special or discussed earlier. "A/An" is used before an indefinite singular noun. "Union leader" is a fixed noun. Hence "the" will be used.
He is the union leader.