It's ______ colder today than it was yesterday. [ ]
A. very
B. more
C. much
D. little
答案:C
从山下到山顶的盘山公路长3千米,小明上山每小时行2千米,下山每小时行3千米,他上、下山的平均速度是每小时[ ]
A.2.5千米
B.1.2千米
C.2.4千米
断齿常由()逐步扩展而成。