Answer:
D
Explanation:
Period is horizontal group, so left to right it does increase. Down the side they are numbered 1-7 and depending on valence electrons they can have different properties
A
Im pretty sure it's A. I MIGHT be wrong so dont quote me on this. THis is what the internet says:
"Atomic Radius. Atomic radii decrease from left to right across a period and increase from top to bottom along a group."
