Because Dong Soo taught his friend Joshua about Korean culture, a reader can infer that

Responses
A Joshua would not need to teach Dong Soo about Joshua's culture.Joshua would not need to teach Dong Soo about Joshua's culture.
B Joshua would be willing to teach others about Dong Soo's culture.Joshua would be willing to teach others about Dong Soo's culture.
C Joshua would be willing to teach Dong Soo about Joshua's culture.Joshua would be willing to teach Dong Soo about Joshua's culture.
D Joshua would be unwilling to teach Dong Soo about Joshua's culture.Joshua would be unwilling to teach Dong Soo about Joshua's culture.

C Joshua would be willing to teach Dong Soo about Joshua's culture.