阅读理解。 One afternoon little David was playing with his friends in the street when he was hit by a motorcycle. He fell and broke his arm. And he was immediately taken to a hospital. There a doctor operated on his arm and put it in a cast (石膏)-David couldn't move it at all. 'You must keep your arm in the cast for a month,' the doctor said. 'That will give your arm a chance to become healthy again.' At the end of a month David went back to the hospital. The doctor cut the cast and took David's arm out of the cast. 'Can you move your arm, David?' he asked. David tried to move his arm. At first it was difficult, but soon he could move it easily. 'Yes, it's fine,' he said. 'Thank you very much.' 'In a few days it will be as good as new,' the doctor said. 'Just exercise it a little.' 'Will I be able to play the violin?' David asked. The doctor smiled. 'Of course you will,' he said. 'You'll have no problems.' 'That is good news,' David said happily. 'Because I couldn't play it at all before.' 1. How was David's arm broken? A. He hurt it himself. B. A motorcycle hit him. C. His friend broke it. D. He fell off a motorcycle. 2. He had to keep his arm in a cast for about _____ days. A. twenty B. thirty C. forty D. fifty 3. The doctor told David to _____ after the cast was taken off. A. keep his arm still B. play the violin C. exercise his arm a little D. ride a motorcycle 4. At last David was pleased because _____. A. he would get a violin B. he would not have to play the violin again C. he would play the violin with his friends D. he thought he would be able to play the violin