Mr. George works at the school lost and found. He works very carefully. Every day, when he gets a lost thing, he takes notes about it. There are pens, books, school uniforms, keys, walkmans and many other things in the lost and found. Most of them are the students’. If you lose your things, it’s easy for you to go to the lost and found for help. But you must tell Mr. George what it is and its color and the day when you can’t find it. I think Mr. George is very helpful, and you will be happy when you find the lost there.

平行四边形ABCD的对角线AC与BD相交于O，则（　　）

连词成句