数列{an}中，已知对任意正整数n，a1＋a2＋a3＋…＋an=2n－1，则a12＋a22＋a32＋…+an2等于 ( ) A. B. C. D.
下图是我国北纬30°植被叶面积指数变化示意图（叶面积指数是指单位土地面积上植物叶片总面积占土地面积的倍数），完成31～32题。 31．造成我国100°
植物在单侧光照射下弯向光源生长，这个现象被解释为“光线能够使生长素在背光一侧比向光一侧分布多”。 为什么生长素在背光一侧比向光一侧分布
如图所示，已知点E、F分别是△ABC中AC、AB边的中点，BE、CF相交于点G，，则CF的长为（ ▲ ）． A．2 B．1.5 C．3
The students were participating __________ an international energy-saving competition between towns in New England and Canada. A. for B. in C. to D.
The strong evidence as well as these new facts _____ prove the prisoner’s innocence the next time the case comes to trial. A. is going to B. are going to
苏格拉底与智者学派的主张的最大区别是有关 A．人的法律关系 B．人的自由与平等 C
Do you think there can be any funds __________ to assist teachers who want to attend the conference? A. effective B. acceptable C. c
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