Make a list of four different events that could change a climax community. For each one, suggest what the area might look like two years after the event.

Explanation:

Finding the (maximum) respective prime powers would yield the answer. Also we need not ... Is perfectly divisible by 720^n? ... So we can say that for any positive value of n it not divisible.

i believe you are right for all except the 3rd ( look at sqdancefan his answer is much better)