Official Explanation from Magoosh

This is a very tough question, since a few of the answer choices seem to work. For instance, the landing could have been (A) strategic and a (D) resounding success…except there are a couple of subtle phrases that argue against this interpretation. It doesn’t make sense to describe a person’s reaction to a highly strategic battle as something that “must have been” a success. If something were so strategic then likely he would have believed that it was a success. This is of course very subtle.

A clearer clue is the idea that Britain had “saved her better infantry” for an imminent landing, meaning that the first landing was so unsuccessful that it appeared that Britain had not sent “her better infantry to fight”. With this interpretation, (E) mere feint, or a pretend movement meant to deceive, fits. And (C) unpropitious, or not favorable or indicating a high level of success, falls into place.

Finally, for the third blank, we need to remember that the first attack was a complete debacle, so much so that Oppenheim thought it was a ruse. Therefore, Oppenheim would be expecting the troops to make a landing in an area that made more strategic sense. (G) not so heavily exposed works best.

FAQ: Why doesn't "unevenly fortified" work for the third blank?

A: "Unevenly fortified" doesn't make much sense here, because the British, if they were indeed saving their troops for another attack, would want to land somewhere that was better protected (not so heavily exposed). Somewhere that is "unevenly fortified" isn't really a good place to attack from. It implies that parts of it are unsafe. "Not so heavily exposed" is a better choice because it more strongly implies a safer location to attack from. Remember that "landing upon" does not mean "attack on." The third blank is talking about an area from which the British are going to attack.