a boxer's left jab的用法和样例：
- Seldom's main weapon is a left jab.
- A great fighter doesn't react that way to a left jab.
- Punching involves quite a few skills,such as the straight left,the left jab,the left hook,the right uppercut,the right cross as well as the combination punching like the one-two.
- He neatly fended off a jab at his chest.
- He had a bruise just below his left eye.