Assertion (A) Chemical messengers are chemicals that enable communications of message between tow neurons or between or between neurons and muscles.
Reason (R) Chemicals enter the cell through receptor.

Options

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

Explanation

To analyze the assertion and reason provided in the question, we can break it down step by step:

### Step 1: Understanding the Assertion (A)
The assertion states that "Chemical messengers are chemicals that enable communications of message between two neurons or between neurons and muscles."

- **Explanation**: Chemical messengers, also known as neurotransmitters, are indeed responsible for transmitting signals in the nervous system. They facilitate communication between neurons and also between neurons and muscle cells, allowing for various physiological responses.

### Step 2: Evaluating the Reason (R)
The reason states that "Chemicals enter the cell through receptor."

- **Explanation**: This statement is partially correct. Receptors are proteins located on the cell membrane that bind to specific chemicals (like neurotransmitters). When a chemical messenger binds to its receptor, it can trigger a response inside the cell. However, the phrasing "chemicals enter the cell through receptor" can be misleading; it is more accurate to say that the binding of chemicals to receptors initiates a series of events that may lead to changes inside the cell.

### Step 3: Conclusion
- The assertion (A) is correct as it accurately describes the role of chemical messengers in communication between neurons and muscles.
- The reason (R) is also correct, but it could be more precisely stated. It does not directly imply that chemicals enter the cell through receptors; rather, receptors facilitate the response to these chemicals.

### Final Evaluation
Both the assertion and the reason are correct, but the reason may need clarification for precision.