The author is not committing circular reasoning. The conclusion is different from the support: although they look similar, when reading closely we can see that the conclusion is about the factual cause of yawning, whereas the support is about people's beliefs.

To make (A) correct, the support would have to be a factual claim that seeing someone yawn is the strongest trigger of yawning. This would have to replace the author's discussion of popular beliefs.

The author does cite historians of popular culture, but fully within their area of expertise. The claim for which these historians are cited is that in the past, a certain belief about the cause of yawning has been widespread. And we can expect historians of popular culture to be experts about common beliefs—that's what popular culture is.

If the author had cited historians of popular culture to support a scientific claim about the cause of yawning, then (B) could be correct. That kind of claim would truly be outside their area of expertise.

The author doesn't draw evidence from particular cases, so (C) can't be correct. It simply doesn't describe the argument the author makes.

The author's evidence is entirely about opinion—that currently and in the past, lots of people believed a particular claim about yawning. And the question at hand is factual—the conclusion is about the actual cause of yawning. What's more, this mismatch makes the argument unconvincing. (D) accurately describes the argument's flaw.

The author only concludes that seeing someone else yawn is "the most irresistible" cause of yawning. That doesn't exclude the possibility of other causes, meaning (E) does not accurately describe the argument. Yawns could still have other causes; as long as they're lesser causes, that's perfectly consistent with the argument.