Which one of the following species does not exist under normal conditions?

Which of the following species has the highest bond order?

Which of the following molecules is paramagnetic?

The formation of molecular orbitals can be described by the linear combination of atomic orbitals. Which one of the following correctly represents the formation of bonding molecular orbital from the atomic orbitals having wave functions $\psi_A$ and $\psi_B$?

What is the correct sequence of bond order for the given species?

Which of the following best describes the given molecular orbital diagram?