Answer: B. 2 electrons
Step-by-step explanation:
Remember the shells. 1s(2), 2s(2), 2p(6), 3s(2), 3p(6) ...
A S shell is always the closest, so it is always 2 electrons.
Looking at a periodic table can help you memorize this pattern. Hope this helps!
(also the Pauli Exclusion principle)