下列有关板块学说原理,正确的表述是( )
A:地球表层是由一块整体岩石组成
B:板块是静止不动的
C:板块与板块交界的地带地壳比较稳定
D:板块与板块交界的地带多火山地震
25+23+720= ____
阅读下列短文,从每小题的三个选项中选出最佳答案
It is morning now. Look at the sun, it rises in the east(东方). Look at the tree, the shadow is long. It is noon now. The sun is high in the sky. It is very hot. Look at the tree. The shadow is short. It is evening now. The sun goes down in the west(西方). Look at the tree, the shadow is long again. It is night now. The moon is high in the sky. There are some stars in the sky too.
物质
a
b
c
d
反应前质(g)
10
2
反应后质(g)
待测
21