水在人体内的作用,下面哪一项的说法是错误的( )
A:水是细胞的主要组成成分
B:物质必须溶解在水里才能运输
C:水在人体内分解,释放能量供生命活动
D:人体各种生理活动都离不开水
自然状况下,鸡有时会发生性反转,如母鸡逐渐变为公鸡。已知鸡的性别由性染色体决定。如果性反转公鸡与正常母鸡交配,并产生后代,后代中母鸡与公鸡的比例是()
如图是一幅触电急救常识宣传画.请你给它配上简要的文字说明.
Sam has got a bike. He goes to school by bike. Amy hasn't got a bike. Her father has got a car. She goes to school in her father's car. Daming hasn't got a bike. He goes to school by bus.