What could be done to change this carbide ion to a neutral carbon atom?

This question is not complete but the completed question is below

What could be done to change this carbide ion to a neutral carbon atom?

(a) remove 2 electrons (b) add 2 electrons (c) remove 4 electrons (d) add 4 electrons

The correct option is c

Explanation:

Elements (with the exception of the noble gases) in the periodic table want to achieve there duplet/octet configuration and hence become stable. They generally do so by accepting/donating electrons. When they accept/gain electron(s), they become negatively charged and when they lose/donate electron(s), they become positively charged.

The symbol for carbide ion is C⁴⁻. It can be deduced from this symbol that carbon has accepted four new electrons. So, in order to become a neutral atom again, these 4 electrons will have to be removed.