— What do you think of this exhibition?
— Great.It's ______ exhibition I' ve ever seen.

Fast food ______ is not always bad for our health, but too much of ______ is not good.

— You remind me ______ Mr. Li. You wear the same jacket.
— Oh, it belongs ______ Mr.Li. He lent it to me.

— I can't learn English. I read my books but I always forget.
— Why not consider ______ flashcards?

Sam is ______ honest boy. If he makes ______ mistake, he will tell his parents.

（2011贵州黔南）三角形两边长分别为3和6，第三边是方程的解，则这个三角形的周长是(            )

（2011四川内江）如图，在直角坐标系中，矩形ABCO的边OA在x轴上，边OC在y轴上，点B的坐标为（1,3），将矩形沿对角线AC翻折，B点落在D点的位置，且AD交y轴于点E.那么D点的坐标为（   ）

（2011浙江温州）如图，O是正方形ABCD的对角线BD上一点，⊙O与边AB，BC都相切，点E，F分别在边AD，DC上．现将△DEF对折，折痕EF与⊙O相切，此时点D恰好落在圆心O处，若DE=2，则正方形ABCD的边长是（    ）

设m>n>0，m²+n²=4mn ，则 的值等于（ ）

当a=-2，b=3，c=-1时，则代数式a²-b²+2bc-c²的值是（     ）