(Answer) (C) 3
Boron is a non-metal with atomic number 5. The electronic configuration of boron atom is [He]2s^22p^1.
Boron atom has the tendency to obtain stable electronic configuration like its nearest noble gas helium by losing electrons. Boron atom usually loses 3 electrons from its outermost electronic shell to form a cation with +3 charge.
Therefore, boron atom loses 3 electrons while forming an ion.
