According to the octet rule, atoms tend to form bonds in order to reach 8 electrons in their outermost shell, this is done in order to stabilize the atom, this is why noble gas, in group 18, usually will not form bonds with other atoms, and will rather live on their own, because they already have 8 electrons. In the picture, we have an atom with 6 electrons in its outermost shell, called valence shell, therefore in order to have 8 electrons and stabilize, the atom will have to gain electrons, 2 to be more specific. The answer will be letter C