Which of the following behaviors may be regarded as impolite when using the chopsticks?

参考解析：

细节理解题。根据倒数第三段第二句“Before the meal, the chopsticks should be placed parallel to one another on the right side of one’s plate or bowl; during the meal, the chopsticks should be placed on the rack or plate after use, not placed casually back on the table”可知，用餐前，筷子应平行摆放在餐盘或碗的右侧；用餐时，筷子应放在用餐后的架子或盘子上，不能随便放回桌上，A项和B项正确；C项在文中没有谈到；根据倒数第四段第三句“When eating, one uses chopsticks or a spoon to transfer the food into one’s own plate or bowl.”可知，用餐时，人们用筷子或勺子把食物转移到自己的盘子或碗里，D项正确。故选C。