Application question

I have almost completed my application for UIUC but I have one section I am unsure about. On the app they ask this: “Do you have a low grade or a drop in grades that you have not already explained?” I got my first C my junior year in a tough class. I had an A my first quarter and a B the second but did not do well on the final and ended up with a C for the semester. Do I explain this on the app?? It sounds like usually you should only explain a poor grade if you’ve had an illness/death in the family—things like that. I wasn’t going to address it but the way this was worded makes me unsure. Any thoughts?