Question

David left the cookies in the oven too long and they became charcoal.

Answer 1

Neither, burned cookies do not turn into charcoal.

Answer 2

Answer:

Cause: David left cookies in the oven for too long.                                                

Effect: as the cookies were in the oven for so long they became charcoal.  

cause in the sentence is the action which leads to that situation whereas effect is the outcome of that situation which was taken place.