I would say A but D could also be said softly
The water was as calm as the forest
hope that help i tried my best
B.........................
It's not a simple sentence: it has more than one clause.
It is also not compound: the two clauses are not independent <span>and a compound has independent clauses.
</span>It is however complex: the two clauses are not independent (<span>While you were on vacation is the dependent clause). This is the correct answer.
(it's not compound-complex because it has 2 and not more clauses)
</span>
Last year, we were near the market.