What is the electron configuration for Be 2+ ions?

Question

1) 1 3) 2-1
2)2 4) 2-2

I also need an explanation for the correct and incorrect answers because I am confused by this problem.

Answer 1

Fill the 1s first. It can hold 2 electrons.
Fill the 2s next. It can hold 2 electrons.
Fill the 2p next (if needed). It can hold 6 electrons.
How many electrons do we need to fit into Be (the neutral atom). The atomic number is 4; therefore, Be atom is
₄Be = 1s2 2s2
For the +2 ion, we remove the last two electrons. So the new configuration for the +2 ion is
1s2.