Answer:
C) comments written in a condescending tone
Step-by-step explanation:
Dr. Collins encourages his students to solve questions and discuss topics he taught in class on his personal website. However, he would prohibit comments written in a condescending tone because they are disrespectful and could discourage students from participating in discussions. The other options, such as comments written in an informal or formal tone or comments using attributed quotes, do not necessarily violate any rules or norms on the website.