Charlie came from a poor village. His parents had 1 money to send him to school when he was young. The boy was very2 . Mr. King lived next to him. He knew it and lent some 3 to him. So the boy could go to school. He studied hard and 4all his lessons. When he finished middle school, Mr King introduced him to his friend in the town,  5 he began to work.

    Once Mr. King was hurt 6  in an accident. He was dying and he asked Charlie to take care of his 7, Sharon. The young man agreed and several years later he married the girl. He loved her very much and tried his best to make8  happy. He often bought delicious food for her. He was good at cooking and he cooked 9 for her. So she became very fat. And one day she found there was something wrong with her heart and she had to go to 10 at once. The doctors looked her over and told her 11 eat meat, sugar, chocolate and things like these. She was afraid 12 the doctor's words , so she wrote all the names of the food on the paper. When she got home, she put the paper on the table and 13. When she came back home that afternoon, she found many kinds of 14 : meat, sugar and chocolate in the kitchen. Charlie was busy 15 there. When he saw her, he said happily, "I bought all the food you like, dear!"

假设你使用的显微镜目镜不变，那么使用以下哪种物镜观察到的范围最大（  ）