How long has the nationwide ban(禁止) on plastic bags been put into practice—__________ the beginning of June.

People in those days liked to believe in computers ________ the world.

一 Mr. Liu Beijing last week一No, but he Beijing with his daughter next month.

up in______ countryside, surrounded by the beautyof _______nature.

He was chosen chairman of the Trade Union and he was happy to ________ the role.[ ]