Kinetic friction may be defined as A. Friction force acting when the body is just about to move B. Friction force acting when the body is in motion C. Angle between normal reaction and resultant of normal reaction and limiting friction D. Ratio of limiting friction and normal reaction

The correct answer is: B. Friction force acting when the body is in motion.

Kinetic friction is the force that opposes the relative motion of two objects or materials that are in contact. It is always directed in a way that opposes the motion, and it is proportional to the normal force between the two objects.

The other options are incorrect because:

• Option A is the definition of static friction.
• Option C is the definition of the angle of friction.
• Option D is the definition of the coefficient of friction.

I hope this helps! Let me know if you have any other questions.