用方框中适当的句子完成对话。 Liu Hua: Good morning, Mum! 1 , Miss Gao. Mrs. Liu: How do you do, Miss Gao? Miss Gao: _2 __ Mrs. Liu: Welcome to our home. Miss Gao: Thank you. Mrs Liu: 3 Please sit down. Miss Gao: __4___ A. How do you do? B. This is my teacher C. Thanks. D. You're welcome.