The answer is B.) The safari stopped at an oasis, a moist fertile spot in the desert.
The appositive phrase is a moist fertile spot in the desert. You can read the rest of the sentence without that part and still have a complete sentence. It describers oasis.
If you're asking what figure of speech, it would be a Simile when using 'like' or 'as' for keywords in the sentence.
1) compound
2) pretty sure the second option is the best one.
3)third option
4)one of the twins
5)third option
6)sentence 3 (I think)
7)no one expected that outcome
8)simple
9)the first sentence given
