What factor primarily links the Indus River Plain to Pakistan’s high agricultural output and population density?

💡 Explanation:

The Indus River Plain is composed of highly fertile alluvial soil deposited by the Indus River and its tributaries. This natural fertility, combined with the extensive canal irrigation system made possible by the flat terrain, is the primary reason it became Pakistan's agricultural heartland and, consequently, its most densely populated region. This question requires analyzing the relationship between the physical geography (soil/water) and human geography (agriculture/population).