I think its A. take action and make the world more stable.
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.
Depending on the context of the letter, you would need an introduction, a greeting, your reason for writing this letter, what you would want to add to your letter, an ending, and your name at the end.
