Answer: d. All of the above are likely causes of confusion in this scenario.
In this situation, it is likely that all of the above were causes for confusion. Nonverbal communication can be very different in different cultures. For example, the reason why the Japanese people looked at the Americans could be related to body language, gender roles, appearance, etc. In terms of verbal communication, the Japanese might be surprised at their language, the topics they discuss, their noise levels, etc. Because communication is so linked to culture, it is good to try to get acquainted with the culture before visiting the country.