Bicycles have been around in our life for more than hundreds of years, but no one knows who ________ the first bicycle.

1. A.
   invented
2. B.
   had invented
3. C.
   has invented
4. D.
   would invent

Bicycles have been around in our life for more than hundreds of years, but no one knows who __________the first bicycle. 

A．invented           B．had invented            C．has invented            D．would invent