Question

Which place would most likely have a low population density?

a. Sahara Desert*** b. Coastal North America c. Southeast Asia d. Western Europe

Answer 1

A. Sahara Desert as its inhospitable. 

Answer 2

A, Sahara Desert.

The coasts of NA have many globally famous and well populated cities, such as Los Angeles, New York City, Seattle, Vancouver, etc.
SE Asia has areas with very high population densities, like in the Phillipines and Indonesia.
Western Europe has a high population density, like in Paris, London, or Madrid.

This leaves Saharan Africa. Do you think many people live there?
So your answer is A.