What is the maximum delay that can occur if four flip-flops are connected as a ripple counter and each flip-flop has propagation delays of t_PHL = 22 ns and t_PLH = 15 ns?

ANS:D - 88 ns

Please clarify that whether the ripple counter is synchronous or asynchronous.

Because when it is asynchronous then the total delay is 4*(tplh+tphl)/2 else it would be only (tplh+tphl)/2;