The correct answer is option 1, which states that "there is one standard time for the whole country."

Let`s dissect each option to understand why option 1 is correct:

Option 1: This statement is correct. India follows Indian Standard Time (IST), which is a single time zone used throughout the country. This means that the same time is observed in all states and union territories of India.

Option 2: This statement is incorrect. The Andaman and Nicobar Islands, as well as the Lakshadweep Islands, follow the same Indian Standard Time (IST) as the mainland of India. Therefore, there are no different time zones within the country.

Option 3: This statement is incorrect. Indian Standard Time (IST) is actually five and a half hours ahead of GMT (Greenwich Mean Time), not behind it. GMT is used as a reference for time across the world.

In conclusion, option 1 is correct as there is indeed one standard time for the whole country, which is Indian Standard Time (IST).