如图所示,一只蜗牛沿着葡萄枝缓慢爬行,若葡萄枝的倾角为α,则葡萄枝对重为G的蜗牛的作用力为( )
A:Gsinα
B:Gcosα
C:G
D:小于G
The students stopped talking__________ the teacher came into the classroom.
放在水平桌面上的水杯,水杯对桌面有压力,下列说法正确的是( )