Answer : 2. "Diamagnetic"
Explanation :

Answer: B) Diamagnetic Explanation: Paramagnetic Molecules :: If the Electronic configuration of a molecule has any unpaired electrons, then that molecule is said to be Paramagnetic. Diamagnetic Molecules :: If the Electronic configuration of a molecule has only paired or spin paired electrons, then that molecule is said to be Diamagnetic.   Here the molecule C2 has all paired electrons in its electronic configuration. So C2 is Diamagnetic. Whereas, B2 molecule has unpaired electrons. So B2 is Paramegnetic.