The bond order is maximum in

The bond order and magnetic property of acetylide ion are same as that of $........$.

The pair of species with the same bond order is

In which of the following sets is the sum of bond orders of the three species maximum?

Consider the following changes $I$ and $II$ as shown in the figure. The correct statements about these changes $(I)$ and $(II)$ in accordance with $MO$ theory are:
$A$) In $(I)$ bond order increases by $0.5$ from the existing value.
$B$) In $(II)$ bond order decreases by $0.5$ from the existing value.
$C$) In both $(I)$ and $(II)$ magnetic property is changed.
$D$) In both $(I)$ and $(II)$ magnetic property is not changed.

The incorrect statement regarding molecular orbital $(s)$ is