A : Transmission of the nerve impulse across a synapse is accomplished by neurotransmitters .
R : Transmission across a synapse usually requires neuro transmitters because there is space , i.e., synaptic cleft, that separates one neuron from another .

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark (1).
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark (2).
C. If Assertion is true statement but Reason is false, then mark (3).
D. If both Assertion and Reason are false statements, then mark (4).

Answer

### Step-by-Step Text Solution

1. **Understanding the Assertion**:
- The assertion states that "Transmission of the nerve impulse across a synapse is accomplished by neurotransmitters."
- This statement is true. Neurotransmitters are chemicals that facilitate the transfer of nerve impulses between neurons.

2. **Understanding the Reason**:
- The reason provided is "Transmission across a synapse usually requires neurotransmitters because there is space, i.e., synaptic cleft, that separates one neuron from another."
- This statement is also true. The synaptic cleft is the gap between two neurons, and neurotransmitters are necessary to bridge this gap and allow the impulse to continue from one neuron to the next.

3. **Linking Assertion and Reason**:
- Both the assertion and reason are true statements.
- The reason correctly explains why neurotransmitters are required for the transmission of nerve impulses across a synapse. The presence of the synaptic cleft necessitates the use of neurotransmitters to transmit the impulse.

4. **Conclusion**:
- Since both the assertion and the reason are true, and the reason is the correct explanation of the assertion, we can conclude that the correct answer is that both statements are true and the reason is the correct explanation of the assertion.