Answer:
B. Cool fact when John White went back to Roanoke where his wife, daughter, and grandson were he found nothing there no sign of any colonists every living there, except the word "Croatoan" carved in a wooden post.
Pachacuti built a strong central government and also took his sons for training to Cuzco which ensured the loyalty.
<u>Explanation:</u>
Moreover, he also kept the local people as rulers which increased their loyalty towards him.
Local administrators were made to collaborate with regional level administrators who looked after justice, land, labour, etc. The regional rulers were told to report to the supreme Inca ruler.
Also, the heirs of the local rulers were kept as prisoners to ensure loyalty of their people.
I think that one of the main ones most of the time is drought as we have such a dry and hot climate. But currently flooding is an issue, in Tasmania we just had the biggest flood since the 1921 floods (Look it up).
Northern parts of Australia are also prone to tropical cyclones