a sick expression的用法和样例：
- The nurse is attending to a sick man.
- No one can feel as helpless as the owner of a sick goldfish.
- One who keeps vigil, as at a sick person's bedside.
- No self-respecting doctor would refuse to treat a sick person.
- A sick person is likely to be fussy about his food.
- Is he so vile as to steal a coat from a sick man?