How do most autosomal recessive alleles that lead to lethal diseases persist in human populations?

A. These diseases only affect individuals who are XY.
B. These diseases usually take effect later in life after people have had children.
C. The disease-causing allele can “hide” in the heterozygous condition.
D. The environment plays a large role in determining whether the gene is expressed.

C. The disease-causing allele can “hide” in the heterozygous condition.