To answer this question, you need to understand the different ancient calendars used in India and Nepal. Let's go through each option to understand why it is correct or incorrect:
Option A) Vikram Samvat - This option is correct. The Vikram Samvat calendar is a widely used calendar in India and the official calendar of Nepal. It is named after the legendary king Vikramaditya and is based on the lunar system.
Option B) Hindu calendar - This option is incorrect. While the Hindu calendar is widely followed in India, it is not the official calendar of Nepal.
Option C) Saka Calendar - This option is incorrect. The Saka Calendar is another ancient calendar used in India, but it is not the official calendar of Nepal.
Option D) Gregorian Calendar - This option is incorrect. The Gregorian Calendar is the internationally accepted calendar system, but it is not specifically associated with India or Nepal.
The correct answer is A) Vikram Samvat. This option is correct because it is the popularly used calendar in India and the official calendar of Nepal.