Billy and Johnny are brothers, but they do not look alike. Which one of the following pairs of factors contributed to this genetic variation?

A- Non-disjunction and mitosis.
B- Cytokinesis and cloning.
C- Crossing over and independent assortment.
D- Asexual reproduction and binary fission.

C- Crossing Over

Explanation:

Crossing over is essentially the gene shuffling and swapping around of genetic information.

A- is false because mitosis describes the building of nonsexual cells. So in terms of genetics, meiosis is the one you're looking for in this scenario.

B- Brothers are not clones.

D- Your parents had to have sex to produce a child. This is not Asexual.

try using substitution:

x + y - 6 = x - y. (i'm not giving you the exact answer). since 0 = x - y, then sub 0 in the equation with x - y. combine your like terms, and then use inverse operations, and you'll have your answer.

: -)