Question

what is bond order of O2 ,B2,CO

Answer 1

Bond order is the number of bonds between a pair of atoms.
The bond order of:
O2 is 2
B2 is 1
CO is 3

Answer 2

The number of bonds between two bonded atoms is called as bond order.

O2 has 2,B2 has 1,CO has 3 bond order