Subnet problem

Hi all,

I need to do a networking address scheme for the information provided below:

Block A = 300 devices
Block B = 600 devices
Block C = 500 devices
Block D = 100 devices
Block E = 200 devices

This is my analysis:

The number of subnets required is 5 (1 subnet for each block)
The number of hosts needed for each subnet are - 300,600,500,100,200 (total= 1700)

Now I was asked to select an internal IP address. Is this selected at random, as far as it is within the class limit?
If I choose class C, is that enough? and why?

Any help would be highly appreciated.
Thanks.