Assertion (A): Human body produces highly toxic substances, which if not eliminated may cause the death.
Reason (R): Excretory substance removes nitrogenous waste from the body.

Options

A. Both A and R are true and R is the correct explanation of A.
B. Both A and R are true but R is NOT the correct explanation of A.
C. A is true but R is false.
D. A is false and R is true.

Explanation

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**: The assertion states that the human body produces highly toxic substances that, if not eliminated, can lead to death. A common example of such a toxic substance is urea, which is produced from the breakdown of proteins in the body. If urea accumulates in the bloodstream, it can lead to a condition known as uremia, which can be fatal if not treated.

**Hint**: Think about what happens when waste products accumulate in the body.

2. **Understanding the Reason (R)**: The reason states that excretory substances remove nitrogenous waste from the body. This is true because the excretory system, which includes organs like the kidneys, plays a crucial role in filtering out nitrogenous wastes (like urea) from the blood and excreting them in urine.

**Hint**: Consider the role of the kidneys and how they help maintain body health.

3. **Evaluating the Relationship Between A and R**: Both the assertion and the reason are true. However, the reason does not directly explain the assertion. While the assertion talks about the consequences of toxic substances, the reason simply states a fact about the excretory system's function without linking it back to the assertion's claim about the consequences of not eliminating these wastes.

**Hint**: Analyze whether the reason provides a direct explanation for the assertion.

4. **Choosing the Correct Option**: Based on the evaluation, the correct option is that both the assertion and the reason are true, but the reason is not the correct explanation of the assertion.

**Final Answer**: The correct answer is the second option: "Both assertion and reason are true, and reason is not the correct explanation of assertion."