生物分类从大到小的等级依次是:____、门、纲、目、科、属、种.
选出与句子内容相符的图片。
① It's going to rain soon. ____ A.
② It's going to snow.____ B.
③ It's raining now____ C.
④ It's going to be windy in Lhasa.____ D.
关于x的函数fx=x3+3x2+3x-a的极值点的个数有( )
综合探究题