What is an example of a single replacement reaction?

The correct option is C $A+BX\to AX+B$
The example of a single replacement reaction is given by the option $\left(C\right)$.
$A+BX\to AX+B$
For example, $Mg$ displaces hydrigen from $HCl$
$Mg+2HCl\to MgC{l}_2+H_2$