Here's why:

* Natural Selection is the process where organisms with traits better suited to their environment survive and reproduce more successfully, passing those traits on to their offspring.

* Inheritance of acquired characteristics was a theory proposed by Jean-Baptiste Lamarck. It suggested that traits acquired during an organism's lifetime (like a blacksmith's strong arms) could be passed down to their offspring. This theory has been largely discredited as it has no evidence to support it.

Let's look at the other options:

* A. Variation among individuals within a population: This is a fundamental principle of evolution by natural selection. Populations are not uniform; individuals have varying traits.

* B. Overproduction of offspring: Organisms produce more offspring than can survive, creating competition for resources.

* C. Differential survival and reproduction: This is the core of natural selection. Individuals with advantageous traits are more likely to survive and reproduce, passing those traits on.

In summary, natural selection relies on variations existing within a population and these variations impacting an individual's survival and reproduction success. It does not rely on traits acquired during an organism's lifetime being inherited.