如图10所示，电源电压保持不变，开关S断开时，电压表示数为2V；开关S闭合时，电压表示数为6V，那么电阻R1∶R2= 。
It was due to her elegant ______ and gentle temper that she has won the respect of her collegues. A. deeds B. behaviors C. a
组成纤维素、纤维素酶和控制纤维素酶合成的DNA的基本组成单位依次是（） A．葡萄糖、葡萄糖和氨基酸 B． 葡萄糖、氨基酸和核苷酸
下列生态因素中不属于非生物因素的是（ ）A.阳光、温度 B.空气、温度 C.水分、土壤 D.寄生虫、病毒
---Look! That woman looks like your mother. ---It ________her. My mother___________Japan_____business. A. can’t ; has been to; for B. may not; has been to; inC
Living in a big city has many _____, such as good schools, libraries and convenient traffic. A. goodness B. advantages C. effects
《秦始皇本纪》载：“秦初并天下，令丞相、御史日：‘……寡人以眇眇之身，兴兵诛暴乱，赖宗庙之灵，六王咸伏其辜，天下大定。今名号不更，无
研究人员同时进行了多种植物激素对豌豆植株侧芽生长影响的实验，结果见下图．请据图回答： （1）比较曲线 可知顶芽对侧芽的生长有抑制作
的形式，指出
分别是(▲)．
B．
C．
D．
