If Both Husband and Wife Are Known to Be Heterozygous

Multiple Choice

If both husband and wife are known to be heterozygous for the autosomal recessive condition of albinism, what is the probability that among their four children, three will be normal and one will have albinism?

A) 27/256
B) 3/4
C) 9/16
D) 13/32
E) 27/64