在下列四支试管中分别加入一些物质，甲试管：豆浆；乙试管：氨基酸溶液；丙试管：牛奶和蛋白酶；丁试管：人血液中成熟红细胞和蒸馏水。上述四
He telephoned the travel agency to three air tickets to London. A．order B．arrange C．take D．book
----- I called you this time yesterday, but there was no answer. ----- Oh, I’m sorry. I ______ dinner at my friends’ home. A. have B. had C. was having D. ha
蜜蜂完全变态发育的正确过程是（ ） A．幼虫→卵→蛹→成虫 B．卵→蛹→成虫 C．卵→幼虫→蛹→成虫 D．卵→蛹→幼虫→成虫
23. Today CCTV offers a great _______ of programs to meet different needs and _______. A. variety; tastes B. many; interests C. deal; likes D. number; habits
A是椭圆长轴的一个端点，O是椭圆的中心，若椭圆上存在一点P，使∠OPA=,则椭圆离心率的范围是_________.
复数，在复平面上对应点不可能位于（ ） A. 第一象限 B. 第二象限 C. 第三象限 D. 第四象限
