Question

Del's good grades were due to regular attendance, good participation in class, and he studied effectively.

A) correct
B) incorrect

Answer 1

Well if Del did participate in class, study effectively and was regularly at attendance than that would be correct in how and why his grades are good.
But if he didn't do those thinks than that would be incorrect.

Sorry but there isn't much detail in order to answer this question, but I would answer correct with the information I was given because if you were regularly at attendance, participated in class, and studied effectively you would tend to get better grades than someone who didn't.

Answer 2

B) incorrect
the last words should say "and studying effectively" because everything else is in present tense
hope this helps!