31. In the past few years, research has suggested that Vitamin D may increase the level of serotonin(血清素), one of the key neurotransmitters influencing our mood, and ________it helps to relieve mood disorders.
24.We have strong __________ for believing that the mine accident in Heilongjiang was due to the poor management.
23.—Hey, dear! Guess what? I’ve got a pay rise! —This ________ a celebration! Let’s go to sing karaoke tonight.
22.I’m terribly sorry to turn you down this time, but I promise I will ________ to you next time.
21.The moment we heard the news of the earthquake, we began to ________ the work to rescue those who were trapped in the building.
Suddenly the idea came to me ____ I might turn to Mr.Smith for help.