Is there a board _____ the wall? ( )
A:on
B:schoolbag
C:about
— is it today?
— It's Monday.
下列物质所选用的材料中,属于有机合成材料的是( )
With the help of the teacher, he decided _______ in class.
如图所示,用一根结实的绳子在两根光滑木棒上绕几圈,一小朋友用力一拉,两位大力士竟撞在一起了.这幅漫画表明了____.