"If students ask more questions, they will understand...

[Biro]

"If students ask more questions, they will understand the lessons better."
I'm not sure what the subject in this sentence is and if it's a simple sentence or a compound sentence, but I think "students" is the subject, and that it's a simple sentence because there's no coordinating conjunction. Correct ?

[Mister Micawber]

The subject of the sentence is 'they', in the main clause. It is a complex sentence, because the 'if' clause is a dependent or subordinate clause.
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Native English teacher at Mister Micawber's