已知集合 $A=\left\{1,3,\sqrt{m}\right\}$ ，B={1，m}，A∪B=A，则m=（   ）

阅读短文，判断下列句子分别符合A、B、C哪一项。

    Hello! My name is Jack. I'm eleven. I'm a student. I study in the Fifteenth Primary School. I'm in Class 4, Grade 5. There are 45 students in my class. They are 22 girls and23 boys. We have English, Chinese, maths and other subjects.

    This morning I was the first one to get to school.John was the second one. Ann and Amy were the third and the fourth. We are in the same class. We have English lessons in the sixth classroom. Our classroom is on the fourth floor of our school building.