题目内容：
根据以下资料，回答题。Before the conference began，a Japanese businessman was introduced to an American businessman at the lounge．The Japanese businessman，arms extending downwards from his shoulders，bowed from his waist toward the American businessman to whom he was just introduced．His eyes were directed ahead，his face showed no particular expression．
The American businessman stood straight．His eyes focused on the Japanese man’S eyes．He smiled and put out his right hand．
Both men smiled briefly in embarrassment．The Japanese man straightened up and put out his right hand．The American withdrew his hand and bowed his head．A broader smile of embarrassment．and some noise from each man-not really words，just some sounds from their throats-indicating discomfort．They were in the course of a conflict of customs；they had different habits for greeting people they were being introduced to．
When people are planning to go to another country,they expect to encounter certain kinds of differences．They usually expect the weather and the food to be different．They expect to find differences in some of the material aspects of life，such as the availability of cars，electricity，and home heating systems.And，without knowing the details，they expect differences in customs．Customs are the behaviors that are generally expected in specific situations．American men，for example，shake hands with each other when first introduced while Japanese men bow．
When introduced to the Japanese businessman，the American businessman put Out his right hand because____． A．he felt a little bit nervous
B．he wanted to express his discomfort
C．he felt a little offended by the Japanese man
D．he wanted to shake hands with the Japanese man
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