Assertion (A): White matter of brain and spinal cord comprises axons.
Reason (R): Axon of a neuron is coated with myelin sheath.

Options

A. Both A and R are true and R is the correct explanation for A.
B. Both A and R are true, but R is not the correct explanation for A.
C. A is true and R is false.
D. A is false and R is true.

Explanation

To solve the question, we need to analyze the assertion and the reason provided:

### Step 1: Understand the Assertion
The assertion states: "White matter of brain and spinal cord comprises axons."
- **Explanation**: White matter is indeed composed primarily of myelinated axons. This is true because white matter appears lighter in color due to the presence of myelin, which insulates the axons and facilitates faster transmission of electrical signals in the nervous system.

### Step 2: Understand the Reason
The reason states: "Axon of a neuron is coated with myelin sheath."
...