Initially, $1|2$
The requests are :
$1\rightarrow 1|2$
$2\rightarrow 1|2$
$4\rightarrow 1|2|4,\,\, Page fault=1$
$5\rightarrow 2|4|5,\,\, Page fault=2$
$2\rightarrow 2|4|5,\,\, Page fault=2$
$1\rightarrow 4|5|1,\,\, Page fault=3$
$2\rightarrow 5|1|2,\,\, Page fault=4$
$4\rightarrow 1|2|4,\,\, Page fault=5$
So, $(C)$ should be the answer