Why is the Kobe-Osaka region of Japan thickly populated?

Presence of a number of industries.

The correct answer is Option (3) → Presence of a number of industries.

Industrialisation: Industrial belts provide job opportunities and attract large numbers of people. These include not just factory workers but also transport operators, shopkeepers, bank employees, doctors, teachers and other service providers. The Kobe-Osaka region of Japan is thickly populated because of the presence of a number of industries.