题干
— It's dangerous to swim in this river.
—Yes, you are right. The government has ______ people not to swim in it.
A：trained
B：warned
C：make
D：encouraged
答案(点此获取答案解析）
B
>m
，甲自由下落1秒后从同一地点再释放乙，如果以乙为参考点，则在它们落地之前，甲的运动状态是( )