If a group of individuals shares a highly similar environment, what effect does this have on the heritability estimate of a characteristic?

If a group of individuals shares a highly similar environment, what effect does this have on the heritability estimate of a characteristic?

a. Heritability will be low.
b. Heritability will be high.
c. Heritability estimates will be unaffected.
d. It is determined by the power of the environmental factors.