A：沼气
B：天然气
C：煤气
D：坑道气
元朝是我国历史上一个重要的朝代，下列不能反映其进步性的一项是( )
半径是2分米的圆，周长和面积是相等的．
—I think teenagers should be allowed to make their own decisions when they have problems at school.
—_______. They're not calm enough, after all.
读课文《我能行》第一自然段，说说贝贝在干什么？
