a bit of string的用法和样例：
- A bit of embrocation will soothe your bruised knee.
- Setting up this business was a bit of a gamble.
- The party was a bit of a damp squib.
- Don't rely on his memory he's a bit of a dreamer.
- Bumping into you like that is a bit of luck.
- I am always a bit of a duffer at maths.