Select all of the following that are true about autosomal recessive inheritance of a human disorder.

a. The disorder typically appears in every generation, and only one copy of the disease-causing allele in necessary to cause the disorder.
b. Both parents of an affected individual carry at least one copy of the disease-causing allele.
c. One or both parents of an affected individual must have the disorder.
d. The disorder is seen more often in males.
e. Heterozygous individuals are called carriers.