In 838,why Was the Japanese Monk Ennin Sent by the Emperor

In 838,why was the Japanese monk Ennin sent by the emperor as part of a delegation to China?

A) to learn the reason for Tang China's success. 
B) to keep many Chinese customs and ideas from being known outside the area.
C) to spy on the Chinese military in advance of a Japanese invasion. 
D) to learn more about Chinese Hinduism.  
E) none of these choices.