_________has one of the most extensive rail networks accounting for nearly 40 per cent of the world’s total.

North America

The correct answer is Option 3: North America

NCERT: " North America has one of the most extensive rail networks accounting for nearly 40 per cent of the world’s total.  In contrast to many European countries, the railways are used more for long-distance bulky freight like ores, grains, timber and machinery than for passengers. The most dense rail network is found in the highly industrialised and urbanised region of East Central U.S.A. and adjoining Canada."