1、Greenhouses_____near coasts can turn plentiful sea water i

1、Greenhouses_____near coasts can turn plentiful sea water into fresh water for crops at relatively lower coasts.
A are built B built C to have been built D having been built
2、We should pay great attention to safety in schools because of frequent reports about accidents ______students got injured or killed while in school.
A in which B for which C which D that
3、I was much impressed by great changes and fast pace of life in Shanghai_______I came to visit this fantastic city.
A at the first time B for the first time C by the first time D the first time
4、If you are travelling ______the customs are really foreign to your own,please do as the Romans do.
A in which B what C when D where