In the past few years, research has suggested that Vitamin D may increase the level of serotonin（血清素）, one of the key nurotransmitters influencing our mood, and ________it helps to relieve mood disorders.
| A．that | B．where | C．what | D．which |
In a sport's team, each player has a clear role, and there are few occasions __________ members are confused or uncertain of their roles.
| A．which |
| B．that |
| C．when |
| D．how |
Please __________ the money and I'm sure it will __________ more than 1，000 yuan.
| A．add; add up |
| B．add up; add up |
| C．add up; add up to |
| D．add to; add up |
Giving up my job to go back to full-time education was a big __________，but now I know it was the best decision I ever made.
| A．project |
| B．commitment |
| C．competition |
| D．ambition |
I can't thank you __________ much because without your help I __________ have won first prize.
| A．too; wouldn't |
| B．very; shouldn't |
| C．enough; might not |
| D．so; couldn't |
A __________ program on TV is calling on people to donate money or other things to the people who have suffered from the flood in Henan Province.
| A．live |
| B．living |
| C．lively |
| D．alive |