The component of contact force normal to the surfaces in contact is called normal reaction. The component parallel to the surfaces in contact is called friction.

Contact force can b resolved into two components. one parallel to contact surface called friction and the other perpendicular to contact surface called normal reaction force which is balanced by weight of the body.these two are action reaction forces

The correct answer is 'D) Normal reaction'.

Explanation:
The component of contact force normal to the surfaces in contact is called the normal reaction. Let's break down this explanation into detail:

1. Contact force:
Contact force is the force that occurs when two objects are in physical contact with each other. When objects touch each other, they exert forces on each other due to the interaction between their molecules or atoms.

2. Normal force:
The normal force is the component of the contact force that acts perpendicular (or normal) to the surfaces in contact. It is the force exerted by a surface to support the weight of an object resting on it.

3. Surfaces in contact:
When two objects are in contact with each other, they have surfaces that are touching each other. For example, when you place a book on a table, the surfaces of the book and the table are in contact.

4. Tension:
Tension is a force that occurs when an object is being stretched or pulled. It is not directly related to the component of contact force normal to the surfaces in contact. Therefore, option 'A) Tension' is incorrect.

5. Friction:
Friction is a force that opposes the relative motion or tendency of motion between two surfaces in contact. It acts parallel to the surfaces in contact and is not the component of contact force normal to the surfaces. Therefore, option 'B) Friction' is incorrect.

6. Gravitational component:
Gravitational force is the force of attraction between two objects due to their masses. It acts vertically downwards and is not the component of contact force normal to the surfaces. Therefore, option 'C) Gravitational component' is incorrect.

7. Normal reaction:
The normal reaction is the force exerted by a surface to support the weight of an object resting on it. It acts perpendicular (normal) to the surfaces in contact. Therefore, option 'D) Normal reaction' is correct.

To summarize, the component of contact force normal to the surfaces in contact is called the normal reaction. It is the force exerted by a surface to support the weight of an object.