题目

How long does it take Amy _________to school every day, do you know?A. walks B. walking C. walk D. to walk 答案：【答案】D【解析】句意：知道Amy每天步行上学花费多长时间吗？根据句型It takes sb time to do sth做某事花费某人时间，故此处用动词不定式to walk，故选D。近似数0.060500的有效数字个数是 [     ]A．6B．5C．3D．2