Which of the following does not affect a population's size?
a. birth rate
c. death rate
b. exchange rate
d. migration rate

The exchange rate is not something that you would talk about in the context of population: it most typically refers to the currency exchange between different countries.- the correct answer is b.

Birth and positive migration rate show the increase in a population size and death rate shows a decrease in the population size.

B. the west has a variety of climates and many different biomes