Rephrase my question

The error isn't that the argument is "appealing to solely factual opinion," it is that the argument "supports its conclusion by appealing solely to opinion in a matter that is largely factual." The conclusion of the argument is: "seeing someone else yawn must be the most irresistible cause of yawning." Why? Well because, "Most people believe that yawning is most powerfully triggered by seeing someone else yawn. This belief about yawning is widespread not only today, but also has been commonplace in many parts of the world in the past, if we are to believe historians of popular culture." Yawning is a physical/biological reaction. Thus, there is most likely a very factual, scientific explanation as to what "is the most irresistible cause of yawning." However, the argument merely supports its scientific conclusion by appealing to a belief held by most people, i.e. opinion. That's why answer choice (D) is the correct answer. The argument "supports its conclusion by appealing solely to opinion in a matter that is largely factual." Hope this helps! Please let us know if you have any other questions.

Thanks again~ and sorry for my mistake