Americans are usually 1) tolerant of non-native speakers who have some 2) trouble
understanding English. But they become 3)annoyed when a person pretends to understand but
doesn‘t 4)really. This 5)creates problems when he misunderstands what is said. No one
wants 6)soap when he asks for 7)soup. So if you don‘t understand what is said to you,
8)admit it and politely ask the person to repeat or explain. All you have to say is, "Excuse me,
would you mind repeating what you said? I didn‘t understand."
Second, it is quite 9)rude to converse with a companion in your native language and
leave your American friends 10)standing there feeling 11)uncomfortable because they can‘t
understand the 12)conversation. The Americans may also feel that you are talking about them
or saying something you don‘t want them to hear. If you have to 13)switch to your native language
to explain something to a non-English-speaking 14)companion, then at least translate for your
American friends so they don‘t feel 15)left out.
原文：http://www.cnblogs.com/wangshixi12/p/4027707.html