Final answer:
A) The introduction of new agricultural techniques and crops, especially from the Americas, led to a population boom in Ming and Qing China by increasing the food supply and allowing more land to be cultivated.
Step-by-step explanation:
The massive population boom during the reign of the Ming and later Qing dynasties can primarily be attributed to A) the introduction of new agricultural techniques and crops. Specifically, the adoption of crops from the Americas, such as sweet potatoes and maize, played a crucial role in augmenting the food supply.
These crops were well-suited to the hilly, dry regions of China and provided abundant calories, thereby supporting a larger population.
Additionally, improvements in agricultural technology during the Song period, which introduced new strains of rice that allowed for two harvests per year and enhanced irrigation methods, contributed to a substantial rise in the population by boosting food production and enabling more land to be cultivated.
These advancements in agricultural practices drove a significant increase in population as they were able to provide the necessary sustenance for a growing society.