Assertion : All derived quantities may be represented dimensionally in terms of the base quantities.
Reason : The dimensions of a base quantity in other base quantities are always zero.

Explanation

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

### Step 1: Understand the Assertion
The assertion states that "All derived quantities may be represented dimensionally in terms of the base quantities."

- **Explanation**: Derived quantities are those that can be expressed using base quantities. For example, velocity (a derived quantity) can be expressed as distance (length) divided by time, which are both base quantities.

### Step 2: Understand the Reason
The reason states that "The dimensions of a base quantity in other base quantities are always zero."

- **Explanation**: Base quantities are independent of each other. This means that when you express one base quantity in terms of another base quantity, the dimension of the first in the second is zero. For example, the dimension of length in terms of mass is zero because they are independent.

### Step 3: Analyze the Truth of Assertion and Reason
- **Assertion**: True, because derived quantities can indeed be expressed in terms of base quantities.
- **Reason**: True, because the dimensions of one base quantity in terms of another base quantity is indeed zero, confirming their independence.

### Step 4: Conclusion
Both the assertion and the reason are true, and the reason correctly explains the assertion.

### Final Answer
Both the assertion and the reason are true, and the reason is the correct explanation for the assertion.

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