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.
—Where did you go on National Day? —Jiuzhai Valley. I ______ to go to France, but the expense was too high.
My close friend Amy was admitted to Oxford University, ______ came as no surprise.
______ I have a quick word with you? Something important has happened.
The presents ______ on my birthday moved me a lot.
Experience doesn't always _____ to the problem we are faced with.