By going through the above criterion we can conclude the following statements
In the first forward trip, Q and R will go and on this trip, Q will row.
Now, R will come back on the 1st return trip and R will row.
In the 2nd forward trip, R and P will go and R will row.
Now, P will come back on the 2nd return trip and P will row.
In the 3rd forward trip, P and S will go and S will row.
So, R rowed Twice. option C)