Sam, our cat, is too lazy to catch mice. what is the appositive in that sentence?

Use who. if it wasn't a question, you could put the he in the blank.  if you can put he or she in the blank, it's who.if you can put him or her in the blank, it's whom.

Where is the answer choices at?

You need to provide more information because i do not know what story it is or character this is referring to.