Biology please help.​

Ialready know the answers to these questions and they are on the attachment. but i just need to know why that answer is the correct one. plz asap! this is for a report that i need to email by 10!

This is a situation in which genes are attached to an organism's sex chromosomes; the sex of an organism influences the expression of a gene.

Which of the following is the earliest era of earth's geologic time scale? cenozoic mesozoic precambrian paleozoic