Assertion (A): In our houses, the current in AC electricity line changes direction 60 times per second. Reason (R): The frequency of alternating voltage supplied is 60 hertz.

Explanation:

Assertion (A): "In our houses, the current in AC electricity line changes direction 60 times per second." An alternating current (AC) completes one full cycle (positive and negative half) in a certain time. In one full cycle, the current changes direction twice (at the zero crossings). If the frequency of the AC supply is 'f' hertz, it means there are 'f' cycles per second. Therefore, the current changes direction 2f times per second. If the frequency were 60 Hz, the current would change direction 2 * 60 = 120 times per second. If the frequency were 50 Hz, it would change direction 2 * 50 = 100 times per second. The statement says it changes direction 60 times per second, which would imply a frequency of 30 Hz (2 * 30 = 60), which is not a standard household frequency. Thus, Assertion (A) is false.

Reason (R): "The frequency of alternating voltage supplied is 60 hertz." This statement is true for many countries, particularly in North America (e.g., USA, Canada) and parts of Asia, where the standard household electricity frequency is indeed 60 Hz. While other regions use 50 Hz, 60 Hz is a valid and common standard frequency for alternating voltage supply. Thus, Reason (R) is true.

Considering both statements: Assertion (A) is false. Reason (R) is true.

This matches option D.

The final answer is D