题目

Many businesses started up by college students have _________thanks to the comfortable climate for business creation. A . fallen off B . taken off C . turned off D . left off 答案：B下列前者为物理性质,后者为化学性质的是A. 汽油易挥发，碘能溶于酒精 B. 铜绿受热易分解，氧气具有氧化性C. 金属铁能导电，钢铁易生锈 D. 酒精能燃烧，金刚石很硬