Solution:

Option (C) 24 is correct.

Explanation:

It is known that,

$\begin{array}{l}
{ }^{n} P_{r}= \\
\frac{n !}{(n-r) !}
\end{array}$

${ }^{4} \mathrm{P}_{4}=4 !=24$ is the four digit numbers that can be formed with the digits $2,3,4,7$ and using each digit only once.

As a result, Option (C) 24 is the correct answer.