第21题: [单项选择]It is well-known that the more old people use their brains, the more mentally active they will be. A. 这件事传开了,老人越多用脑,智力就越灵活。 B. 大家知道了,老人更多动脑,主动性更强。 C. 众所周知,老人用脑越多,智力就越活跃。 D. 众所周知,老人用脑越多,智力会更活跃。 参考答案:C 答案解析:[难点分析] well-known表示“众所周知”;the more...the more.一意为“越来越…”。