1. 那个男孩根本不懂礼貌。
2. 瞪着眼睛看人是不礼貌的。
3. 他走路的样子很不自然。(in a ... manner)
Key:
1. The boy has no manners at all.
2. It's bad manners to stare at people.
3. He is walking in a rather unnatural manner.