认真学习本堂课定语从句的用法,填写正确的关系代词、关系副词完成以下定语从句: 1、This is the professor _____1______ taught me physics in 1980. 2、The hospital ____2______ was built six years ago was closed yesterday. 3、He talks about teachers and schools _____3________ he had visited. 4、Do you know the student ______4_______ was praised at the meeting. 5、1949 is the year _____5_______ the People's Republic of China was founded.