Why were nepal and bhutan generally able to remain independent when their neighbors were taken over by outsiders

Humans have survived and thrived in mexico city by using technology to create greater access to land. when the spanish conquered the aztec capital, tenochtitlan, in the 16th century, they built mexico city by draining the lakes and filling in the lake water to create more arable land for agriculture. this technique of land reclamation has continued to be fundamental to human civilization in mexico city. 

How is this a question? where are the answer choices?

Ones bigger then than the other

The answer is winds.