题目

——Where is your school bag?——I think I ______ it during the concert so it might still be in the symphony hall.A. dropped B. threw C. fell 答案：A 已知：如图，在正方形ABCD中，点E、F在对角线BD上，且BF＝DE． （1）求证：四边形AECF是菱形． （2）若AB＝2，BF＝1，求四边形AECF的面积．