What is an allele?
A. form of gene
B. a type of virus
C. a group of chromosomes
D. a group of proteins

(this is from apex)

A) form of gene

Explanation:

An allele is one of the different variants of a gene. It is one of the two or more genes found on the same locus on a chromosome which determines a specific trait in an organism. An allele can be dominant or recessive. A dominant allele is the allele that has the ability to mask the effects of a recessive gene when it is paired with the recessive gene while a recessive lacks the ability to express itself in the presence of a dominant allele. For a recessive allele to express itself, it must occur in a homozygous form.

c. establishing proper sleep hygiene