Strongest collision resistance test?
A. Find two identical messages with different hashes


This is fundamentally impossible, assuming you're talking about a regular hash and not a keyed hash (like HMAC). As hashes are deterministic, two identical messages will always result in an identical hash.


  B. Find two identical messages with the same hash


This is not only possible, but guaranteed. Two identical messages will always have the same hash.


  C. Find a common hash between two specific messages


Assuming "specific message" refers to a message that you generate, this would be a collision attack. Such attacks are done against the hash function itself, not any existing message. A collision attack generates two messages which differ but which result in the exact same hash output.


  D. Find a common hash between a specific message and a random message


This implies a preimage attack, which is similar to a collision, but you only get to control one message. It's also far harder to exploit than a collision attack because you do not have as much freedom.