题目

—Lin Ming ______baseball.He plays chess(国际象棋)．—Oh，it isn't good for him.A．don't play                               B．doesn't playC．doesn't have                           D．don't have 答案：B 点拨：考查一般现在时。Lin Ming是第三人称单数形式，助动词应用doesn't，排除A、D两项。由“He plays chess(国际象棋)．”可知前句可能为“林明不打棒球”，排除C项。故选B项。已知：如图，AB是⊙O直径，OD⊥弦BC于点F，且交⊙O于点E，若∠AEC=∠ODB．（1）求证：BD是⊙O的切线；（2）当AB=10，BC=8时，求BD的长．