Explanation:

Paramagnetism is the property of the substance to get attracted towards the magnetic field. The substances which have unpaired electrons are attracted to the magnetic field. The substances which do not have unpaired electrons are diamagnetic, i.e., they are not attracted to the magnetic field.

Let's check the electronic configuration of the given molecules to identify which one is paramagnetic and which one is diamagnetic.

a) B2: The atomic number of boron is 5. The electronic configuration of B2 is (σ1s)2(σ*1s)2(σ2s)2(σ*2s)2(π2py)2(π2px)1. Here, there is an unpaired electron in the π2px orbital. So, B2 is paramagnetic.

b) C2: The atomic number of carbon is 6. The electronic configuration of C2 is (σ1s)2(σ*1s)2(σ2s)2(σ*2s)2(π2py)2(π2px)2. Here, all the electrons are paired. So, C2 is diamagnetic.

c) O2: The atomic number of oxygen is 8. The electronic configuration of O2 is (σ1s)2(σ*1s)2(σ2s)2(σ*2s)2(π2py)2(π2px)2(π*2py)2(π*2px)1. Here, there are two unpaired electrons in the π*2py and π*2px orbitals. So, O2 is paramagnetic.

d) None: Since both B2 and O2 are paramagnetic, the answer is None.

Therefore, the correct answer is option 'B' which is C2 as it is diamagnetic and not paramagnetic.