Chloro compound of vanadium has only spin magnetic moment of $1.73BM$. This vanadium chloride has the formula:

[Atomic number of $V=23$]

The correct option is C $VC{l}_4$
Magnetic moment $=\sqrt{n(n+2)}$

where $n=$ number of unpaired electrons

$\sqrt{n(n+2)}=1.73$

$\therefore n=1$
Electronic configuration of $V$ is $\left[Ar\right]4s^{2}3d^3$. For only one unpaired electron it has to be $V^{4+}$.

Hence, the formula of vanadium chloride is $VC{l}_4$.

Therefore, the correct option is $B$.