Bunuel wrote:

If N is a positive integer, what is the tens digit of N?

(1) N is divisible by 25.

(2) N is divisible by 16.

Given: N > 0 and integer

Required: Tens digit of N?

Statement 1: N is divisible by 25

N = 25 or 50

Hence we cannot tell the tens digit.

INSUFFICIENT

Statement 2: N is divisible by 16

N = 16 or 32

We cannot tell the tens digit

INSUFFICIENT

Combining Statement 1 and Statement 2:

N is a multiple of both 16 and 25

Hence N is a multiple of 400

N = 400, 800, ...

In all the cases, the tens digit will be 0

SUFFICIENT

Option C