A:①②③
B:①③④
C:①②④
D:②③④
一只空心球总体积为V,球腔容积为V/2,当腔内不灌水时,它在水中有一半露出水面,若将球腔内注满水再放入水中,则()
下列四组河流中,流进黄土高原的是( )
—May I help you?You seem to be having some problems.
—________,thanks. I think I can manage.
①细胞核 ②叶绿体 ③线粒体 ④细胞质基质