The correct answer is: C. Action of solar radiations particularly cosmic rays on carbon dioxide present in the atmosphere.
Radiocarbon is a radioactive isotope of carbon with the symbol 14C and atomic number 6. It is a naturally occurring trace radioactive gas composed of 14C atoms. It is produced in the upper atmosphere by cosmic rays, which convert nitrogen atoms into 14C. The half-life of 14C is about 5,730 years, which means that half of the 14C atoms in a sample will decay into 14N in 5,730 years. This decay is what makes 14C useful for dating.
The 14C produced in the atmosphere is absorbed by plants through photosynthesis. Animals eat plants, and so 14C is also found in animal tissues. The amount of 14C in the atmosphere is relatively constant, so the amount of 14C in living things is also relatively constant. However, when something dies, it stops taking in new 14C. The 14C in the dead thing then decays at a constant rate. By measuring the amount of 14C in a dead thing, scientists can determine how long ago it died.
The other options are incorrect because they do not explain how 14C is produced in the atmosphere. Option A is incorrect because it states that 14C is produced by the collision between fast neutrons and nitrogen nuclei present in the atmosphere. However, 14C is not produced by this process. Option B is incorrect because it states that 14C is produced by the action of ultraviolet light from the sun on atmospheric oxygen. However, 14C is not produced by this process either. Option D is incorrect because it states that 14C is produced by lightning discharge in the atmosphere. However, 14C is not produced by this process either.