[A]: The biennial plants live for two years.
[R]: They flower in both years.

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 Biennial Plants:**
- Biennial plants are those that complete their life cycle in two years. They typically grow vegetatively in the first year and then flower and produce seeds in the second year.

2. **Analyzing the Assertion (A):**
- The assertion states: "The biennial plants live for two years." This statement is true because biennial plants, such as carrots and cabbages, indeed have a life cycle that spans two years.

3. **Analyzing the Reason (R):**
- The reason states: "They flower in both years." This statement is false. Biennial plants do not flower in both years; they usually flower only in the second year after a period of vegetative growth in the first year.

4. **Conclusion:**
- Since the assertion (A) is true and the reason (R) is false, the correct relationship between the two is that the assertion is correct but the reason is not a correct explanation for the assertion.

5. **Final Answer:**
- The correct option is C: "A is true, but R is false."