Each process needs $2$ drives
Consider this scenario
$\begin{array} {|c |c| c| c| c|}\hline P_{1} & P_{2} & P_{3} & P_{4} & P_{5} & P_{6} \\ \hline 1 & 1 & 1 & 1 & 1 & 1\\ \hline \end{array}$
This is scenario when a deadlock would happen, as each of the process is waiting for $1$ more process to run to completion. And there are no more Resources available as max $6$ reached. If we could have provided one more $R$ to any of the process, any of the process could have executed to completion, then released its resources, which further when assigned to other and then other would have broken the deadlock situation.
In case of processes, if there are less than $6$ processes, then no deadlock occurs.
Consider the maximum case of $5$ processes.
$\begin{array} {|c| c| c| c| c|}\hline P_{1} & P_{2} & P_{3} & P_{4} & P_{5} \\ \hline 1 & 1 & 1 & 1 & 1 \\ \hline \end{array}$
In this case system has $6$ resources max,and hence we still have $1$ more $R$ left which can be given to any of the processes, which in turn runs to completion, releases its resources and in turn others can run to completion too.
Answer (B).
