Answer:
a.) A dietary supplement of cholecalciferol (Vitamin D3)
Explanation:
Vitamin D is an important vitamin that helps in the absorption of calcium, which is one of the fundamental blocks of bones. Vitamin D, naturally can be synthesized in the body when stimulated by Ultraviolet radiation from the sun, upon exposing the skin to sunlight.
As a result of shorter days and long, darker nights during winter, people living in cold climates hardly get enough exposure to sunlight, and as such, the body is not able to naturally synthesize vitamin D. Vitamin D deficiency result in bone problems, as calcium absorption reduces.
A dietary supplement of cholecalciferol will do just fine to solve this problem, as it contains Vitamin D3.