I believe it is C, though I am not entirely sure. A compound sentence is two separate sentences combined with a conjunction, so I'm pretty sure that's correct.
Well to understand this better, let us determine what is
most closely referred here about the clause “waiting for the wave”.
From reading the sentence we can see that since Jim was
waiting for the wave he didn’t notice something was happening to him. So there
is a connection between the clause and the verb. So this an adverb clause.
Answer:
<span>adverb clause</span>
