Cuttlefish appear to be surprisingly ______ blank at exercising self-control: in a 2021 study conducted by

Choice D is the best answer because it most logically completes the text’s discussion of self-control in cuttlefish. In this context, "competent" means capable. The text describes a study in which cuttlefish demonstrated an ability to exercise restraint by waiting for a favorite treat instead of eating a meal that was already available to them. That is, by delaying gratifiion, the cuttlefish in the study demonstrated that they were capable of, or competent at, exercising self-control.

Choice A is incorrect because nothing in the text suggests that in demonstrating self-control, cuttlefish are "awkward," or lacking skill or grace. If anything, the text indies that cuttlefish appear to be surprisingly skilled at exercising self-control. Choice B is incorrect because in this context, "imaginative" would mean creative, and there’s nothing in the text to suggest that cuttlefish demonstrate creativity. Instead, the text focuses on the fact that cuttlefish seem to be capable of exercising restraint and self-control. Choice C is incorrect because in this context, "manageable" would mean capable of being controlled. Although the text indies that the cuttlefish in the study demonstrated restraint by waiting for a favorite treat instead of devouring a readily available meal (which suggests their ability to control themselves), it doesn’t suggest that cuttlefish are thus also able to be managed or controlled by others.