两条直线相交成四个角，如果其中的一个角是直角，那么其他三个角都是直角。

生物的性状就是（　　）

化工生产中含Cu²⁺的废水常用MnS（s）作沉淀剂，其反应原理为Cu²⁺（aq）+MnS（s）⇌CuS（s）+Mn²⁺（aq）．一定温度下，下列有关该反应的推理正确的是（　　）

    Tom was only seven years old. He likes watching ____ very much. He ____ went to the movies before. One day, he ____ to have a try. When getting to the cinema, he bought a ticket (票) and went in. ____ after two or three minutes, he came out, and bought the second ticket and went in. After a few minutes, he came out again and bought the third ticket. 

    Then a girl ____ about him and asked, “Why do you buy so many tickets? How many friends do you meet?” “No, I have no friends here, but a woman always stops me at the door and tears (撕) my ticket.”