Why did STP not place port 3/12 in blocking mode instead?

While deploying a new switch, you accidently connect ports 3/12 and 3/18 together, creating a loop. STP detected it and placed port 3/18 in blocking mode. Why did STP not place port 3/12 in blocking mode instead?

A.
Port 3/12 was already up and forwarding before the loop was created.

B.
Port priority is based on lowest priority and lowest port number.

C.
You connected the wire on port 3/18 last.

D.
None of the above, it is purely random.