四、Read and choose. Nannan 到 Dongdong 家做客，他们都说了什么？请你读一读，选择合适的选项补全对话。
Dongdong: Hello, Nannan.
Nannan: 1. ______
Dongdong: Dad! Mum! This is Nannan.
Father and Mother: Nice to meet you, Nannan.
Nannan: 2. ______
Dongdong: Nannan, this is my grandfather.
Grandfather: How do you do?
Nannan: 3. ______
Dongdong: Nannan, this is my grandmother.
Grandmother: Welcome (欢迎), Nannan!
Nannan: 4. ______
A. Nice to meet you too.
B. Thank you.
C. Hi, Dongdong.
D. How do you do?

C ; A ; D ; B