The correct answer is A complex sentence
Step-by-step explanation:
In grammar, a compound sentence differs from a complex sentence because compound sentences include two or more independent clauses, while complex sentences include at least one independent clause and one dependent clause, which is a clause that does not express a complete idea and therefore needs another sentence to stand.
In the case of the sentence "After staring at each other for a few minutes, the snakes slithered away" this includes an independent clause "the snakes slithered away" and one dependent clause "After staring at each other for a few minutes" because this does not express a complete idea and depend on the second sentence, which is also shown by the use of the conjunction "after" that is a subordinating conjunction. Thus, this is a complex sentence.