Can NiMH type AA battery charger be used for other types like AAA, C, or D (all NiMH)?
You need to consider their current handling capability as well. This increases in order AAA AA C D.

It is safe to charge a higher capability cell from a lower capability charger.

So you will be able to safely charge AA C and D.

AAA may be able to be charged by the same charger but you need to check the specification of the battery and the charger, checking that the battery can tolerate the charge current provided by the charger.

There is a good article on NiMH charging here http://www.powerstream.com/NiMH.htm