The letter is from my sister, ______is working in Beijing. 

 Evidence has been piled up ________ drinking water after getting up in the morning contributes to one's health.

It is reported that there are various reasons _____more and more people feel depressed at this time of year.

Doris' success lies in the fact _________ she is co-operative and eager to learn from others. 

Many young people in the West are expected to leave __    could be life' s most important decision -- marriage -- almost entirely up to luck.