a chain smoker的用法和样例：
- From his appearance we may safely conclude that he is a chain smoker.
- He used not to smoke, but now he is a chain smoker.
- You run a greater risk if you are a chain smoker.
- He is a heavy drinker and a chain smoker.
- Henry is a chain smoker, consuming at least five packs a day.
- Tom is a chain smoker, consuming at least five packs a day.