Which of the following molecules is linear?

Among the compounds shown below,which one reveals a linear structure?

The molecules having square pyramidal geometry are

In a regular octahedral molecule $MX_6$,the number of $X-M-X$ bond angles of $180^{\circ}$ is:

Which of the following is not linear?

$SbF_5$ reacts with $XeF_4$ and $XeF_6$ to form ionic compounds $[XeF_3]^+ [SbF_6]^-$ and $[XeF_5]^+ [SbF_6]^-$ respectively. What are the molecular shapes of the $[XeF_3]^+$ and $[XeF_5]^+$ ions,respectively?