Assertion : The rate of reaction is always negative .
Reason : Minus sign used in expressing the rate shows that concentration of product is decreasing .

Options

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

Explanation

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

### Step 1: Analyze the Assertion
The assertion states: "The rate of reaction is always negative."

- In chemical kinetics, the rate of a reaction is defined as the change in concentration of reactants or products over time.
- The rate of reaction is typically expressed as a positive value, indicating the speed at which reactants are converted into products.
- While the change in concentration of reactants is often represented with a negative sign (indicating that their concentration is decreasing), the rate itself is not negative.
- Therefore, the assertion is **incorrect**.

### Step 2: Analyze the Reason
The reason states: "Minus sign used in expressing the rate shows that concentration of product is decreasing."

- The minus sign is indeed used when expressing the rate of change of reactants to indicate that their concentration is decreasing over time.
- However, for products, the change in concentration is expressed with a positive sign, indicating that their concentration is increasing over time.
- Therefore, the reason is also **incorrect**.

### Conclusion
Since both the assertion and the reason are incorrect, the correct answer to the question is that both statements are false.

### Final Answer
Both the assertion and the reason are incorrect. Therefore, the correct option is **Option 4**.

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