Assertion: Sigmoid growth curve consists of four parts.
Reason : Lag phase is called as grand phase of growth.

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 the Assertion**: The assertion states that the sigmoid growth curve consists of four parts. This is indeed true. The four parts of the sigmoid growth curve are:
- Lag phase
- Log (or exponential) phase
- Diminishing growth phase
- Stationary phase

2. **Understanding the Reason**: The reason given is that the lag phase is called the "grand phase" of growth. This statement is incorrect. The "grand phase" of growth is actually the log phase, where the growth rate is at its maximum.

3. **Conclusion**: Since the assertion is true (the sigmoid growth curve does consist of four parts), but the reason is false (the lag phase is not the grand phase of growth), we conclude that the assertion is true and the reason is false.

4. **Final Answer**: Therefore, the correct answer is that the assertion is true and the reason is false.

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