To find the retarding force necessary to stop the object, we can use Newton's second law of motion, which states that the force acting on an object is equal to the mass of the object multiplied by its acceleration. In this case, the acceleration is the change in velocity over time.

1. Identify the given values:
- Mass (m) = 2 kg
- Initial velocity (u) = 4 m/s
- Time (t) = 1 s

2. Calculate the acceleration:
- Final velocity (v) = 0 m/s (as the object needs to be stopped)
- Using the formula v = u + at, we can rearrange it to solve for acceleration (a):
v = u + at
0 = 4 + a * 1
a = -4 m/s²

Note: The negative sign indicates that the acceleration is in the opposite direction of the initial velocity, which is necessary to stop the object.

3. Calculate the retarding force:
- Using Newton's second law of motion, F = ma
- Substitute the values:
F = 2 kg * (-4 m/s²)
F = -8 N

Note: The negative sign indicates that the force is in the opposite direction of the initial motion, which is necessary to stop the object.

4. Answer:
The retarding force necessary to stop the object in 1 second is 8 N (option C).

Explanation:
When an object is in motion, it requires a force to change its state of motion. In this case, the object is sliding with a velocity of 4 m/s, and we need to stop it in 1 second. To do so, a retarding force is required, which acts in the opposite direction of the object's motion.

By applying Newton's second law of motion, we can calculate the acceleration of the object, which is found to be -4 m/s². The negative sign indicates that the object is decelerating or slowing down.

Using the formula F = ma, we can then calculate the retarding force. By substituting the mass (2 kg) and acceleration (-4 m/s²) into the equation, we find that the retarding force is -8 N. The negative sign indicates that the force is acting in the opposite direction of the object's initial motion.

Therefore, the correct answer is option C, 8 N.