A:arrived; died
B:had arrived; would lose
C:arrived; would have lost
D:has arrived; could have lost
为探究燃烧的条件,设计如图甲、乙两个实验.请回答:
(1)乙和甲相比,乙的优点是____ .
(2)两个实验中,红磷的作用是____.
“苏湖熟,天下足”的谚语说明当时全国最重要的粮仓是( )
在长24cm,宽15cm的长方形中,能剪____半径为3cm的圆.