The question is - which are the complex sentences in this paragraph?
In order to answer this, you first need to know what complex sentences are. A complex sentence is a sentence that contains ONE independent clause and AT LEAST one dependent clause (although there may be more). Having that in mind, the correct answers are the following:
1. Although it was dark, he still hadn’t turned the van’s lights on.
2. Through my translator I enquired why, yet I immediately wished I hadn’t.