The correct answer is: D. Does not move at all.
The resultant of the forces acting on a body is the vector sum of all the forces acting on the body. If the resultant of the forces is zero, then the body will not accelerate. If the body is not accelerating, then it will either be moving at a constant velocity or not moving at all.
If the body is moving at a constant velocity, then it can be moving in a straight line or a curved path. However, if the body is not moving at all, then it must be stationary. In this case, the resultant of the forces acting on the body must be zero.
The other options are incorrect because they all describe situations in which the body is accelerating. If the body is accelerating, then the resultant of the forces acting on the body cannot be zero.
A. Rotates: If the body is rotating, then it is accelerating. This is because the velocity of the body is changing as it rotates. The resultant of the forces acting on the body must be non-zero in order to cause this acceleration.
B. Moves with variable velocity in a straight line: If the body is moving with variable velocity in a straight line, then it is also accelerating. This is because the velocity of the body is changing as it moves. The resultant of the forces acting on the body must be non-zero in order to cause this acceleration.
C. Moves along a curved path: If the body is moving along a curved path, then it is also accelerating. This is because the velocity of the body is changing as it moves. The resultant of the forces acting on the body must be non-zero in order to cause this acceleration.