For reference, this is TFS problem 528 in the 2011 booklet. The solution process is found in MERM 13 page 18-18. Look at figure 18.15. It shows how to add capacity for pumps in parallel. In this case, you have three identical pumps so, the operating point moves up the system curve in additive fashion. This is basically a logic question. One pump delivers a FLOW of 210 (whatever units that is) at 38 ft (so you can rule those two answers out) and three pumps in parallel will produce flow that is roughly 3x that. You also know that the flow and head is going to be MORE than the head that is produced by one pump at the intersection of the system curve (38), so you can also rule out 30ft as well. So you know you need to move UP the system curve to some point. The only reasonable answer is the HEAD that corresponds to what you think the flow might be (which is roughly 3x 210 = 630). That puts you at an operating head that is not only closer to 65 than other option in the list, but 65 is the only remaining LOGICAL number given, because the head is not additive like the flow is. A head of 210 is not achievable with these pumps in parallel. If the pumps were in series, then the 210 answer comes more in play. So, be aware of how easy it would be for them to change this problem to the other answer, just by changing the question to series instead of parallel.