What Was the Main Reason for the Tokugawa Refusing to Establish

What was the main reason for the Tokugawa refusing to establish diplomatic relations with China?

A) They did not want to upset the Korea monarchy
B) They did not want to learn Chinese in order to communicate with the imperial court
C) They did not want to acknowledge Chinese political or ideological superiority
D) They were not permitted to send embassies by Ietmitsu's edicts.