A better shelter and A. clean water lead to growth of global population.
Explanation:
Availability of a good shelter and clean water both help an individual lead a healthy life. The shelter protects him from external environmental factors that may be harmful to his existence. These factors include sunlight, rains, lightning, etc.
Clean water keeps the water-borne diseases away and helps the individual maintain hygiene which is ultimately necessary for his physical well-being. Thus, the availability of shelters and clean water increase the life expectancy and ultimately result in global population growth.
