Alleles can contain the code for:
a. only recessive genes.
b. only the same version of a gene.
c. different genes but of a similar type.
d. the same gene, but different versions.

D. the same gene, but different versions.

Explanation:

Because an allele is an alternative form of a gene, meaning two alleles codes for a gene.

One can be dorminant and the other recessive or both dorminant and or both recessive.

Hope it helps.

the correct answer is sex-linked recessive.

i just took the test