题目

As a __________ boy, Liangliang, crosses the river every school day. but he is not afraid.          A. seven years old     B. seven-year-old     C. seven-years-old 答案：B20．目前已知我国境内最早懂得人工取火的远古人类是（　　）A．元谋人B．北京人C．山顶洞人D．燧人氏