短文改错。

     This autumn my class went to Dalian to go the camping. We arrived at a sandy beach with a well view of the sea. We set up our tents on the sandy beach, when night fell we made a fire to give us light and kept us warm. All the classmates sat around them, talking and laughing. Several hours late, Li Mei and I went

back to the tent to have a chat. We stayed up all of night. We found that we two had a lot of common. For instance, we both like the same singers and have great enthusiasm for physics. The fire and the stars see

our happiness. What I wished time would stop at that moment!

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在票据允许转让、流通的情况下，为保障收款人的权益，规定票据转让时要由转让人在票据背面签字，这种情况称为( )。

A．背书

B．委托

C．代理

D．审批