A: The zygote develops into a multicellular organisms.
R: Each cell is totipotent.

Options

A. If both As and R are correct and R is correct explanation of As
B. If both As and R are correct but R is not correct explanation of As
C. If As is correct, R is wrong
D. If both As and R are wrong.

Answer

### Step-by-Step Solution:

1. **Understanding the Assertion**: The assertion states that "the zygote develops into a multicellular organism."
- A zygote is formed when a male gamete (sperm) fertilizes a female gamete (egg). This fertilized egg is a single diploid cell that will undergo multiple rounds of cell division (mitosis) to develop into a multicellular organism.

2. **Understanding the Reason**: The reason states that "each cell is totipotent."
- Totipotent cells have the ability to differentiate into any cell type, including all the cell types needed to form a complete organism. In the case of the zygote, all its cells are totipotent in the early stages of development.

3. **Connecting Assertion and Reason**: The assertion and reason are connected because the totipotency of the zygote's cells is what allows it to develop into a multicellular organism.
- Since each cell can give rise to a complete organism, it explains how the zygote can undergo division and specialization to form various tissues and organs of the multicellular organism.

4. **Evaluating Truthfulness**: Both the assertion and the reason are true.
- The zygote indeed develops into a multicellular organism, and the cells of the zygote are totipotent, which is essential for the development process.

5. **Conclusion**: Therefore, the correct answer is that both the assertion and reason are true, and the reason correctly explains the assertion.