steal matter friend valuable attend

Sandy：Mom，I’m really worried．
Mom：Why？What’s the （56） ______ ？
Sandy：I can’t find my schoolbag．
Mom：Well，where did you last put it？
Sandy：I can’t remember!I （57） ______ a concert yesterday so it might still be in the museum hall．
Mom：Do you have anything （58） ______ in your schoolbag？
Sandy：No，just my books，my pink hair band and some tennis balls．
Mom：So it can’t be （59） ______ ．
Sandy：Oh，wait!I went to a picnic after the concert．I remember I had my schoolbag with me at the picnic．
Mom：So could it still be at the park？
Sandy：Yes．I left early，before the rest of my （60） ______ ．I’ll call them now to check if anybody has it．