Why is it wrong to understand north-south extent as total coastline in India's size?

Because north-south extent is directional distance and coastline is length along the sea

North-south extent and coastline describe two different geographical measurements. North-south extent is the distance from the northernmost part of a country to its southernmost part, measured mainly in a north-south direction. Coastline is the length of the boundary where land meets the sea, including the shape of the coastal edge. These measurements use different ideas and cannot be treated as the same quantity.

Thus option A is correct because it clearly distinguishes directional distance from length along the sea. Options B, C, and D are incorrect: the two measurements are not always equal, a coastline is not a percentage by definition, and north-south extent is not area. Careful reading of geographical terms prevents confusing distance, boundary length, and area.

This is a Class 9 Geography question. Chapter: India – Size and Location. Topic: Size.