Based on the octet rule, boron will most likely form a ion. based on the octet rule, boron will most likely form a ion. b3- b+ b2+ b2- b3+

The answer to this question would be: b3+

Based on octet rule, atoms tend to give or take electrons by forming an ion until it has eight valence electron. 
An atom with valence electron less than 4 will tend to lose the electron and form a cation. Boron is an atom with atomic number 5 which have 3 valence electron. So, Boron should lose 3 of it valence electron and form a +3 cation.