题目

听下面一段独白，回答以下小题。【1】Where did western culture begin?A. In western Europe. B. In Ancient Greece. C. In Rome.【2】What influenced the North American culture most in recent centuries?A. Arts. B. Science. C. Government.【3】What has provided a new source for western values?A. Modem literature.B. The moving population.C. The invention of television and the Internet.【4】What is the speaker probably doing?A. Giving a lecture. B. Conducting a TV show. C. Hosting a radio program.13．如图，AB为⊙O的直径，AD为弦，∠DBC=∠A．（1）求证：BC是⊙O的切线；（2）连接OC，如果OC恰好经过弦BD的中点E，且tanC=$\frac{1}{2}$，AD=3，求直径AB的长．