单选题 《复合题被拆开情况》 My sister and I looked forward to new clothes for the New Year. But one day my mother said, "Listen, children. We don’t have enough money now. So only one of you can get new clothes. " The silence (寂静) lasted for a few minutes. My tears (眼泪) were coming out. " OK, I have an idea," my sister said. " I’ll write ’new clothes’ on a piece of paper and ’nothing’ on another. We cast lots (抽签) to decide. " I agreed. While she was writing at the table, I found her clothes were old and she had grown too big for the clothes. I looked at my own. They were old, but still the right size for me. "Pick one," my sister said. I picked one and opened it. Two words ran into my eyes: NEW CLOTHES. I forgot my sad feelings and jumped up. A few days later, I ran into the sitting room in my new clothes where my mother and my sister were reading. My sister gave me a smile and went on reading. My mother called me to her side and showed me two pieces of paper. On each of them was written: NEW CLOTHES.《问题》：Why did the writer’s sister suggest casting lots?