7. In a cross with a homo zygous, grey, female moth and a homo zygous, black, male moth, all of the progeny are grey. In a cross with a homo zygous, black, female moth and a homo zygous, grey, male moth, all of the progeny are black. What is the best explanation for this? (2 words)

Due to dominant trait.

Explanation:

The best explanation for this result is that grey colour is dominant trait due to which all of the progeny appears grey while in the second example, black colour is dominant trait which appears in the all the offspring of moth. In the offspring, only that trait becomes visible which is dominant while the trait which does not appear is known as recessive trait so that's the reason due to which grey in the first and black colour in the second becomes visible.

the answer is sex-linked recessive.