A:①③
B:②④
C:③④
D:①④
The workers ____ (build) a new bridge near my house last year and I guess they will finish it next month.
如图所示,在倾角为37°的固定斜面上静置一个质量为5kg的物体,物体与斜面间的动摩擦因数为0.8.sin 37°=0.6,cos 37°=0.8.求: