Questions 18-20 are based on the following dialogue given by Professor Robert Watson who was answering questions on a radio phone program on the subject of learning a foreign language. You now have 15 seconds to read Questions 18-20. What advice was given by Professor Watson7

单项选择题The languages of the so-called undeveloped or uncivilized groups fall behind the Western languages in______.

单项选择题A coronary bypass is an operation______.

单项选择题What’s the speaker’s impression of the advertisement in America when he first arrived there

单项选择题A．survivedB．sunkC．damagedD．built

单项选择题The text is mainly, about ______.