What unit do they usually use to measure stars distance

astronomical unit, or A.U.

Explanation:

it is about 93 million miles or 150 million kilometers

answer: a. a gene that causes a specific trait.

i'm gonna put a couple so you can chose from

explanation:

if you know the fur color of the offspring mice, you can use the ratios to identify the genotypes of the parents.

if either parent mouse passes a dominant allele, the offspring will have black fur.

if the parental mice has two different fur color (i.e white and black) , the color of the offspring's fur would be either black, white, or the combination of both (grey)

hope this : )