Given below are two statements: one is labeled Assertion (A) and other is labeled Reason (R).

Assertion (A): The rate of appearance of new forms is linked to the life cycle or the life span.     

Reason (R): In microbes variant population would appear as new species within days, where as fish or fowl would take million of years as life span of these animals are in years.

In the light of above statements, choose the correct answer from the options given below.

The assertion states that the rate of appearance of new forms is linked to the life cycle or the life span. This assertion is generally true in the context of evolutionary processes. The speed at which new species or variants arise can be influenced by the duration of the life cycle or life span of the organisms involved.

However, the reason provided suggests that in microbes, variant populations can appear as new species within days, whereas in fish or fowl, it would take millions of years due to their longer life spans. This reasoning is correct explanation for the assertion. Also, the time it takes for new species to emerge is influenced by various other factors, including reproductive rates, mutation rates, environmental pressures, and selective forces, not just the life span of the organisms.