It's two years since they ____ each other, and they are going to get married next month. [ ]

A. were in love with

B. fell into love with

C. have loved

D. fell in love with

盛装无腐蚀性的纯气及标准混合气体的钢瓶减压阀一般采用（）减压阀。

A、不锈钢

B、黄铜

C、易燃气专用

D、氧气专用