— They're books.
A:Are these English books?
B:Are those English books?
C:How do you spell it?
D:What're these in English?
两个滑轮完全相同,其重力均为20N.分别用如下图所示的两种方式,将重400N的物体以相同的速度匀速提升了10m,不计摩擦和绳重,则下列判断正确的是()
下列哪项是藻类、苔藓、蕨类植物所具有的共同特征( )