Two sentences joined with a coordinating conjunction and a comma from a:

a. compound sentence
b. complex sentence
c. comma splice
d. run-on

Two sentences joined with a coordinating conjunction and a comma form a compound sentence. If it were a complex, it would have a dash. If it were a comma splice, it would have a dash and a dash. If it were a run-on, it wouldn't have either, just a lot of and in it.

Hope this helps. :D

Istrongly feel d is the answer but c is also a strong possibility