题目

It was Monday. Mrs. Smith’s dog was hungry, but there was not any meat in the house. Thinking about that there was no better way， Mrs. Smith took a piece of paper, and wrote the following words on it: “Give my dog half a pound of meat.” Then she gave the paper to her dog and said gently: “Take this to the butcher (屠夫), and he’s going to give you your lunch today.” Holding the piece of paper in its mouth, the dog ran to the butcher’s. It gave the paper to the butcher. The butcher read it carefully, recognized that it was really the lady’s handwriting and soon did 使用显微镜时，如果光线太强，应 [     ]A．放大光圈，用平面镜 B．放大光圈，用凹面镜 C．缩小光圈，用平面镜 D．缩小光圈，用凹面镜