Why Are People of Ashkenazi Jewish Descent More Likely to Be

Why are people of Ashkenazi Jewish descent more likely to be carriers of the mutations that cause Tay-Sachs and Gaucher disease?

A) The environment of Eastern Europe increased their risk of developing a mutation.
B) The common diet shared by these people has reduced their genetic diversity.
C) Bottleneck effects have reduced the genetic diversity in this population.
D) Being heterozygous for these diseases allowed them to survive cholera.