That's onychophagia. Is it a) Picking your nose b) Biting your nails or c) Talking very loudly Those are all very bad habits. I'm going to go for a) picking your nose.

A. 挖鼻孔 B. 咬指甲 C. 大声讲话这些习惯都不怎么好，我选A挖鼻孔。