Answer:
choice a
Explanation:it would make sense if you say he dinosaurs have gone extinct, but we still don know the reason for their extinction. hope this helped. have a nice day!!
Answer:
It's the first one
Explanation:
Compound sentences are made up of two independent clauses, either joined by a conjunction or a semicolon.
Pretty sure the second one would just be incorrect grammar, and then the third one is a dependent clause because of the word "after."
Hope this helps!
