What should come in place of the question mark (?) in the given series?
991 989 985 979 971 ?

The correct answer is 961.

Let us analyze the given number series to find the logic/pattern governing the terms:

$991,989,985,979,971,?$

Let us calculate the difference between consecutive terms:

$991-989=2$

$989-985=4$

$985-979=6$

$979-971=8$

We can observe that the differences subtracted from each term are consecutive even numbers: 2, 4, 6, 8, ...

Following this pattern, the next difference to subtract from 971 should be 10.

$?=971-10=961$

Thus, the number that replaces the question mark (?) is 961.