根据句子意思,用括号中所给词的正确形式填空,每空填一词。
Seven ____ (twelve) of the students have taken part in the tree-planting activity since Monday.
如图,在平行四边形ABCD中,添加下列条件不能判定平行四边形ABCD是菱形的是( ).
如图,△ABC≌△BDE,若AB=12,ED=5,则CD的长为( )