Brainliesttt asap!me : )

which of the following is a reasonable ground-state electron configuration?

1s22s22p63s2
1s22s22p63s23d4
1s22s22d102p3
1s22s22p32d6

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!

Which is an example of a vestigial structure? a: paw of a lionb: wing of a birdc: appendix of a humand: tail of a cat(i think it's a but i'm not sure)

15. what can be inferred from the fact that there is little diversity in the form of mc1r gene found among individuals from equatorial africa?