Which subnet mask will place all hosts on Network B in the same subnet with the least amount of wasted addresses?

Refer to the exhibit.

Which subnet mask will place all hosts on Network B in the same subnet with the least amount of
wasted addresses?

A.
255.255.255.0

B.
255.255.254.0

C.
255.255.252.0

D.
255.255.248.0

Explanation:
310 hosts < 512 = 29 -> We need a subnet mask of 9 bits 0 -> 1111 1111.1111 1111.1111
1110.0000 0000 -> 255.255.254.0