________ in Tibet for ten years, he has been accustomed to the life and the climate there.
| A．He has worked | B．Having worked |
| C．He has been working | D．Working |
The theory most scientists objected to in the end .
| A．being proved to be of significance | B．was proved to be significance |
| C．proving to be significant | D．proved to be significant |
He knew the problem was serious and undertook to look into it he reached the office.
| A．suddenly | B．immediately | C．abruptly | D．shortly |
To my delight, the snakes, carefully, turned out to be no trouble and all went well according to the plan.
| A．monitoring | B．being monitored | C．having monitored | D．monitored |
Catch the star that holds your fate , ______that forever twinkles within your heart.
| A．one | B．the one | C．it | D．that |
We have been excavating layers of ash almost six metres thick, which suggests that they the fire burning all winter.
| A．should keep | B．might have kept | C．should have kept | D．might keep |