Is 203.10.93.30 a valid Host ID after subnetting?

Yes, it's a valid host.

A. Yes, it is a valid host ID

30 can be constructed by adding 16, 8, 4 and 2. So if we set the last byte as 00011110. Since the first five bits are for subnet, you can think the subnet number as 00011 or 3, and the host number is 110 or 3 again.

203.10.93.11111000

so ip203.10.93.30 comes under subnet ID 203.10.93.16

so 203.10.93.30 is valid host