A:There are many rulers on the table.
B:There are many books on the table.
已知△ABC的周长为48cm,最长边与最短边之差为14cm,另一边与最短边之和为25cm,求△ABC各边的长.
如图“绿叶在光下制造有机物”的实验现象,说明光合作用特性有( )
①需要水;②需要光;③需要叶绿体;④产生淀粉.