Which one of the following is the subnet mask equivalent of

Which one of the following is the subnet mask equivalent of /17?

A. 255.255.255.192

B. 255.255.0.0

C. 255.255.1.0

D. 255.255.128.0

E. 255.255.255.128

D. 255.255.128.0 is the equilent of subnet mask /17 and it has 15 host nits and the the address in subnet is 32768 = 2^15.

I has 512 subnets.