Answer: Option (a) is the correct answer.
Explanation:
Resources which are created by human beings are known as man-made resources.
For example, glass, rayon, nylon etc are all man-made resources.
Whereas resources which are naturally created are known as natural resources.
For example, wind, air, water etc are all natural resources.
Thus, we can conclude that out of the given options time is not a natural resource.
