图所示曲线反映的城市绿地具有的一项作用是（ ）。 Ａ 防风固沙，降低沙尘暴的发生频次 Ｂ 吸烟滞尘，净化空气 Ｃ 调节气温，改良城市小
某溶液中只含有Na+， Al3+，Cl-，SO42- 四种离子，已知前三种离子的个数比为3∶2∶1，则溶液中Al3+和 SO42-的离子个数比为（ ） A．1：2
—What do you think of his teaching? —No one teaches ________ than him. A．good B．well C．better D．the best
在某一电路中，保持电压不变，电流I（安培）与电阻R（欧姆）成反比例，当电阻R=5欧姆时，电流I=2安培． （1）求I与R之间的函数关系式；（2）当电流I
Many people catch a cold in the springtime or fall. It makes us wonder. If scientists can send a man to the moon, why can’t they find a way to deal with the common cold? The answer is easy. There ar
A:My name is Marry. B: I am Jenny.___ A.What’s your name? B.Who are you? C.Hello!D.Nice to meet you!
－You look a bit worried. Do you need any help? －Yes. The task is ______ I could do myself. A. less than B. more than C. no less than D. no more tha
是否存在正整数m使得f(n)＝(2n＋7)·3n＋9对任意自然数n都能被m整除，若存在，求出最大的m的值，并证明你的结论；若不存在，说明理由．
