In which field is the most practical effect of India's longitudinal extent seen?

Local time and Indian Standard Time

The governing concept is the relationship between longitude and time. Earth rotates 360° in about 24 hours, so it turns through 15° in one hour, or 1° in approximately four minutes. India extends across nearly 30° of longitude, producing a local-time difference of close to two hours between its eastern and western regions. To avoid the administrative confusion that many local times would create, the country follows one Indian Standard Time based on 82°30′ E longitude. Therefore, option A is correct. Soil colour and texture depend mainly on parent material, climate and vegetation; river-water salinity depends on dissolved minerals and water conditions; mountain height depends on geological structure and erosion, not directly on longitudinal extent.

This is a Class 11 Geography question. Chapter: India - Location. Topic: Standard Meridian of India and time zones.