【简答题】Whales are ______ ____ as mammals ( 哺乳动物 ) . ( classif y)
【单选题】_____ my surprise, when the students saw this film. they all shouted _____ surprise.
【简答题】When the students saw their teacher , they suddenly stopped ______ { talk } with each other.
【单选题】I saw the students ___ on the chairs in the classroom.
【简答题】Come vengono classificate le monete?
【单选题】有下列结论: (1)命题 总成立,则命题 总成立 (2)设 则 p 是 q 的充分不必要条件 (3)命题:若 ab =0,则 a =0或 b =0,其否命题是假命题。 (4)非零向量 满足 ,则 的夹角为 其中正确的结论有( )
【单选题】有下列结论: ①命题p: x∈R,x 2 >0总成立,则命题 p: x∈R,x 2 ≤0总成立; ②设p: ,q:x 2 +x-2>0,则p是q的充分不必要条件; ③命题:若ab=0,则a=0或b=0,其否命题是假命题; ④非零向量 和 满足 ,则 与 的夹角为30°。 其中正确的结论有 [ ]
【简答题】电路如图所示,晶体管导通时 U BE =0.7V, β =50, U CES =0.1V。 试分析 U I 为0V、1V、3V三种情况下三极管的工作状态,及输出电压 u o =?
【单选题】All the students and their class teacher ______ interested in the film they saw yesterday evening. [ ]
【单选题】有下列结论: (1)命题p:?x∈R,x 2 >0总成立,则命题?p:?x∈R,x 2 ≤0总成立. (2)设 p: x x+2 >0,q: x 2 +x-2>0 ,则p是q的充分不必要条件. (3)命题:若ab=0,则a=0或b=0,其否命题是假命题. (4)非零向量 a 和 b 满足 | a |=| b |=| a - b | ,则 a 与 a + b 的夹角为30°. 其中正确的结论有( ...