Which of the following is a common cause of strep throat?

Strep throat is primarily caused by a bacterial infection, specifically Streptococcus pyogenes, which is a type of group A Streptococcus. While viral infections, such as those that cause the cold and flu, can cause similar symptoms in the throat and lead to conditions like pharyngitis, they are not the primary cause of strep throat itself.

However, it's important to recognize that viral infections can predispose individuals to secondary bacterial infections, including strep throat. Thus, while both viruses and bacteria can lead to throat issues, the classic cause of strep throat directly is from the streptococcal bacteria.

With this in mind, the best answer in the context of common throat infections is the one that aligns with the most prevalent cause of strep throat being linked back to bacterial infections, while also acknowledging the role that viruses can play in throat discomfort, albeit not specifically strep throat.