Which of the following molecules has a bond order of 2.5?

Bond order is a measure of the number of chemical bonds between two atoms in a molecule. It is calculated as (Number of bonding electrons - Number of anti-bonding electrons) / 2. For the molecule NO (nitric oxide): The number of bonding electrons is 5 (1 from N and 2 each from the 2 O atoms). The number of anti-bonding electrons is 2 (1 each from the 2 O atoms). The bond order is calculated as (5 - 2) / 2 = 3 / 2 = 1.5. Therefore, the correct answer is Option D: NO, and it has a bond order of 2.5.