An important reason for China’s rapid population increase in the seventeenth and eighteenth centuries was A the introduction of new crops from the Americas
B the end of the bubonic plague in asia
C the widespread adoption of the European three-field system
D Unprecedented immigration from the Mughal and Ottoman Empires

the introduction of new crops from the Americas

Explanation:

The rapid population increase in China in the seventeenth and eighteenth centuries was due to the introduction of new crops from the Americas.

Food crops like maize, tomatoes, sweet potatoes, beans etc were brought into China which led to major developments accompanied with migration and population growth.