Question 19 is based on the passage you have just heard.

    The topic of my talk today is gift-giving. Everybody likes to receive gifts, right? So you may think that gift-giving is a universal custom. But actually the rules of gift-giving vary quite a lot. And not knowing them can result in great embarrassment. (19) In North America, the rules are fairly simple. If you're invited to someone's home for dinner, bring wine or flowers or a small item from your country. Among friends, family and business associates, we generally don't give gifts on other occasions except on someone's birthday and Christmas. (20) The Japanese, on the other hand, give gifts quite frequently, often to thank someone for their kindness. The tradition of gift-giving in Japan is very ancient. There are many detailed rules for everything from the color of the wrapping paper to the time of the gift presentation. And while Europeans don't generally exchange business gifts, they do follow some formal customs when visiting homes, such as bringing flowers. The type and color of flowers, however, can carry special meaning. Today we have seen some broad differences in gift-giving. I could go on with additional examples, but let's not miss the main point here. If we are not aware of and sensitive to cultural differences, the possibilities for miscommunication and conflict are enormous. (21) Whether we learn about these differences by reading a book or by living abroad, our goal must be to respect differences among people in order to get along successfully with our global neighbors.

(19). What does the speaker say about gift-giving of North Americans?

解析：根据文章可知，在北美，一般只在生日和圣诞节才会给朋友、家人、商业伙伴送礼物。因此D项（他们只在特殊的场合赠送礼物）符合题意。