a crowd of lookers -on的用法和样例：
- I saw a crowd of magazines and papers on her desk.
- I see a crowd of magazine and papers on her desk.
- He did the deed in view of a crowd of people.
- A crowd of people were looking on.
- I saw a crowd of magazinespapers on her desk.
- A crowd of cattle were dotted around the grass land with a little boy sitting on a rock.