Have you ____ (消化)everything that is important in the book.
关于速度和加速度的关系,下列说法中正确的是( )
如图,将矩形ABCD的四个角向内折起,恰好拼成一个无缝隙无重叠的四边形EFGH,EH=12cm,EF=16cm,则边AD的长是( )