The doctor handed me my medicine and said sorry to me because his register   had already closed. He asked if I would mind using the register at the front of the store. I told him not to worry and walked up front. One person was in line ahead of me, a little girl no more than seven with a bottle of medicine on the counter  . She held a little green and white coin purse closely to her chest  . The purse reminded me of the days when, as a child, I liked dressing myself up in my grandma's clothes. One day, wearing her large clothes and hat, I went out to buy something. I gave a fake  dollar to the shop owner, but he handed back some real coins for my purse. "Keep the change!" he told me with a smile. Now, with both hands shaking, the little girl pulled out a dollar bill and some coins for her medicine. As she tried to count her money, I could see right away that she was about a dollar short. Quickly, I put a dollar bill onto the counter. The child collected her change into her coin purse and ran out. As I walked to my car, I felt a tug  on my shirt. There was the girl, looking up at me with her big brown eyes. She gave me a smile, and put out her little hand. It was full of coins. "Thank you," she said. "That's OK," I answered, smiling. "Just keep the change!" The doctor said sorry to the writer because   _  .
his register had broken down his register had closed he was busy he had used up his medicine