_________ many times, he finally understood it.
| A．Told | B．Telling | C．Having told | D．Having been told |
He 20 dollars for his old bike the other day.
| A．paid | B．took | C．spent | D．offered |
It is much easier to talk about social change than to .
| A．bring it on | B．bring it about | C．bring it up | D．bring it out |
This is a story completely by him, so don’t rust him.
| A．discovered | B．invented | C．found | D．known |
Historical experience can as a most important source of information.
| A．serve | B．use | C．regard | D．prove |
Have a good rest, you need to your energy for the tennis match this afternoon.
| A．have | B．save | C．hold | D．get |