Succession is differentiated into two types, primary and secondary. Secondary succession occurs after natural or man-made disturbance that results to disruption or removal of some nutrients and life from the previous community. Some of the natural disturbances that can lead to succession include: wildfire, tornado, and defoliating insects.
The theme is the writer's view of or comment about the subject. The answer to your question is D. I hope this is the answer that you are looking for and it comes to your help.
Scientific theories can never be proven true beyond all doubt; they can only be supported by a wide body of evidence. Only one of the statements that follow uses the term theory in its correct, scientific sense.