“三北”防护林的主要作用是 ( )
A．防止沙尘暴袭击北京
B．防风护田，保持水土
C．调节大气湿度
D．防止黄河下游的水土流失
参考答案：B
I was too careless.If only I ___ my car!
A．hadn't lost
B．would not have lost
C．didn't lose
D．haven’t lost
