A classmate sent me a message the other day, but I didn't see it at that time. I just saw it. Should I reply?

You have to look at this from two aspects: first, how do you get along with your classmates? You had a good time as a classmate, but later you had less contact with them. The second is whether the news content has any influence on you. In fact, you can turn a blind eye to the information, but according to normal analysis, your relationship is not that good. Generally, direct telephone contact will be made. I suggest you reply a message! Explain the reason, but also out of courtesy, not that you are stingy.