Given below are 4 molecular species/ions. Identify the species/ion which exhibits diamagnetic nature.

$$[\mathrm{A}]=\mathrm{N}_2^{+} \quad[\mathrm{B}]=\mathrm{O}_2^{-} \quad[\mathrm{C}]=\mathrm{B}_2 \quad[\mathrm{D}]=\mathrm{C}_2$$

Which of these represents the correct order of decreasing bond order?

Pick up the correct statement.

Total number of $$\sigma$$ and $$\pi$$ bonds in ethene molecule is