[A]: Evolution is descent with modification.
[R]: Evolution is derivation of new species of plants and animals from those existed in past.

Options

A. If both A and R are true and R is the correct explanation of A
B. If both A and R are true but R is not the correct explanation of A
C. If A is true and R is false
D. If both A and R are false

Answer

**Step-by-Step Solution:**

1. **Understanding Evolution:**
- Evolution refers to the changes in species over time. It is a process through which species adapt to their environments, leading to the emergence of new species from common ancestors.
- The concept of evolution was popularized by Charles Darwin, who defined it as "descent with modification."

2. **Assertion Analysis ([A]):**
- The assertion states that "Evolution is descent with modification." This means that species evolve by changing over generations, which can lead to the development of new traits or characteristics.

3. **Reason Analysis ([R]):**
- The reason states that "Evolution is the derivation of new species of plants and animals from those that existed in the past." This aligns with the assertion, as it explains how species can evolve from common ancestors over time, resulting in new species.

4. **Connecting Assertion and Reason:**
- Both the assertion and the reason are interconnected. The assertion provides a general definition of evolution, while the reason gives a specific example of how evolution occurs through the derivation of new species from ancestral forms.

5. **Conclusion:**
- Both the assertion ([A]) and the reason ([R]) are true, and the reason correctly explains the assertion. Therefore, the statement is valid.