“Darwin teaches us that life _________ continually ________ to keeping up with a changing Earth.” The expert explained.

-Why does the lake smell terrible?
-Because large quantities of water      .

-----This returned Chinese scholar has become one of the top experts in this field.
-----Yes, I know him very well. He _____ in Africa with wild animals for eight years.

Tom，together with Mary and Alice，______swim this afternoon．

Father______for London on business upon my arrival，so I didn't see him．

This new method of teaching      for the time being in our school. It will be carried out all________over the city.
A. is experimenting        B. is experimented  C, is being experimented D. has been experimented

Recently Peter________to do his homework, and instead insists on wasting his time playing com-puter games, which extremely annoys his father.

So long as Peter goes all out to do the work, I don't mind how long it _____ him to complete it.

As I know, it is five years since Mary ____ in the south.

The policeman came up to the lonely house with the door open, ________ there for a while and
   then entered it.