15SOS is a code that was used in an old form of communication called Morse Code. It is a call or signal for help.15.1code名词，密码;
学习英语，注重平时的单词、短语的积累，而对于短语，同学们就要做到能够有效地区分各个短语的意义，比如“be angry baout”与“be careful about”，两个短语，就中间一个单词不同，意义就大不相同，前者表示“因某事而愤怒”，后者表示“当心、注意”。
Most of the students are all ears in the class and few of them listen with half an ear. 课上，多数学生都在专心听讲，少数几个没有认真听。
Some people are always coming up to perfect strangers and asking them what they do。有些人总爱和完全不认识的人搭讪，询问人家的职业。
