What is the Standard Meridian line of India?

Which one of the following longitudes is the standard meridian of India ?

The Indian Standard Time Meridian does not pass through

Standard Indian Time (Meridian Longitude 82° 30') passes through which of the following towns?

Indian Standard Time (IST) is ahead of Greenwich Mean Time (GMT) by:

If it is 12.00 Noon in India, on which meridian wil it be 7.00 am of the same day?