All of the following have an OCTET of electrons except о
S-1
O
N-3
O
Be+2
O
Br-1

full octets live in noble gas world so you need to be whatever your charge is away from there in steps on the periodic table so s-1 is the one that falls short as it is 2 moves away from Ar which is its closest Noble gas

Explanation:

d.) circle motion requires a force to give it a centripetal acceleration.

the answer is b & c i believe : )