_____ his research paper, Professor Reagan experienced various hardships and loneliness for nearly half a year．
| A．Accomplishing | B．To accomplish |
| C．Accomplished | D．Having accomplished |
These natural parks are very important for preserving many animals, which would ______ run the risk of becoming extinct(灭绝的)．
| A．otherwise | B．other than | C．therefore | D．in another way |
The girl didn’t know who ______ for the broken vase.
| A．will be blamed | B．blamed | C．was to blame | D．blames |
______ with the size of the whole earth, the highest mountain does not seem high at all.
| A．When compared | B．While comparing |
| C．Compare | D．Comparing |
-- How long do you think it will be ______ the bus arrives here?
-- No more than five minutes.
| A．when | B．before | C．since | D．after |
Making a proper choice ______ the future will probably make much difference in our life.
| A．concerning | B．to concern | C．concerned | D．having concerned |