They are putting too much carbon dioxide into the atmosphere, ______ prevents heat from escaping from the earth into space.              

My sister will never speak to others like that ________they say something unpleasant to her .

All the dishes in this menu， _____ otherwise stated， will serve two to three people. 

In our school, some students are active______ some are shy, yet they can be good friends with one another. 

I still remember the days___ I spent ______ with you in Beijing．