"Emperor Zhengzong, being deeply concerned with agriculture, came to know that the Champa rice was drought resistant and that the green lents of india were custom their heavy yield and large seeds. Special envoys, bringing precious things were dispatched with a view to securing these varieties. When the first harvests were reapedin
the autumn, the emperor called his closest ministers to taste them and compose poems for Champa rice and Indian green te
Shu Wenying Buddhist monk, China, eleventh century CE
Which of the following made possible the Chinese cultivation of the staple crops described in the ln the passage