海康威视红外球型摄像机在安装时，墙壁至少能承受7倍智能球加支架等附件的重量。（）
参考答案：错
—What have you learned from your experience in Thailand?
—Well, meeting people from another culture ______ be very difficult．
A．must
B．can
C．should
D．shall
如图所示，将一光滑球放在挡板和斜面之间，球重力为G，斜面倾角为θ．试求挡板和斜面对小球的支持力．
