一、填空题1.关于物体的平衡,下列说法中正确的是 ( )A.物体处于平衡状态时,一定不受外力作用 B.物体在共点力作用下处于平衡状态时,合外力必为零C.物体在三个非平行力作用下平衡时,此三个力的作用线必交于一点D.有固定转动轴物体的平衡条件是力矩的代数和等于零 First, fill in the blank 1. On the balance of objects, the following statement is correct () A. When the object is in balance, it must not be affected by external forces B. In the case of a total force under the balance of state, the combined force will be Zero C. When the object is balanced by three non-parallel forces, the line of action of the three forces must intersect at point D. The equilibrium condition of the object with the fixed axis of rotation is the algebra of the moment and equal to zero