Assertion (A) It is impossible to determine the exact position and exact momentum of an electron simultaneously.
Reason (R) The path of an electron in an atom is clearly defiened.

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 and R is false
D. Both A and R are false.

Explanation

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**: The assertion states that it is impossible to determine the exact position and exact momentum of an electron simultaneously. This aligns with the Heisenberg Uncertainty Principle, which is a fundamental concept in quantum mechanics.

2. **Defining the Heisenberg Uncertainty Principle**: According to the Heisenberg Uncertainty Principle, the more accurately we know the position of a particle (like an electron), the less accurately we can know its momentum, and vice versa. Mathematically, this is expressed as:
\[ \Delta x \cdot \Delta p \geq \frac{\hbar}{2} \]
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