--- Why don’t you ask him for help? You _____ be good friends.

--- We have disagreements and we haven’t talked to each other for a long time.

A．are used to

B．are used for

C．are used as

D．used to

将少量金属钠分别投入下列物质的溶液中，有气体放出，且溶液质量减轻的（  ）

A．水

B．稀盐酸

C．硫酸钾溶液

D．硫酸铜溶液