The force which tries to bring the body back to its mean position is called
(A) deforming force
(B) restoring force
(C) gravitational force
(D) buoyant force

Hint
It is required to be known that a black body or blackbody is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence. The name "black body" is given because it absorbs radiation in all frequencies, not because it only absorbs: a black body can emit black-body radiation. This is a kind of electromagnetic radiation emitted by any object that has a non-zero temperature. Similarly, a human body temperature of 98.6 degrees Fahrenheit corresponds to a blackbody radiation frequency of about 32 terahertz, which is in the infrared part of the spectrum. Based on this concept we have to write this answer.

Complete step by step answer
We know that,
At the extreme position, kinetic energy is zero and we know to throw out Simple Harmonic Motion.
K.E + P.E = constant
Where, K.E is Kinetic Energy,
P.E is Potential Energy.
So, P.E. should be maximum at the extreme position.
The restoring force acts then to try and bring back the body to its mean position.
Therefore, the correct answer is Option B.

Note
Thus, we can be sure that a blackbody is a theoretical or model body which absorbs all radiation falling on it, reflecting or transmitting none. It is a hypothetical object which is a perfect absorber and a perfect emitter of radiation over all wavelengths.
It is required to know that so a black hole can only be in equilibrium with a gas of radiation at a finite temperature. Since radiation incident on the black hole is absorbed, the black hole must emit an equal amount to maintain detailed balance. The black hole acts as a perfect blackbody radiating at this temperature. Some examples of blackbody radiators that emit visible light or whose radiation is used for other processes include the electric heaters, incandescent light bulbs, stoves, the sun, the stars, night vision equipment, burglar alarms, warm-blooded animals, etc.