Fill in the blanks. Complete the dialogue. 补全对话。

A: Hi, Li Ming! Nice to meet you!       

B:    1   .

A: Welcome to Canada.                  

B:    2   .  

A: Do you like Canada?                     

B:    3   . 

A: Do you live in Beijing?                  

B: No,    4   .

A:    5   ?                             

B: I'm twelve years old.    

a. Thank you            

b. Nice to meet you, too            

c. I live in Shijiazhuang   

d. How old are you          

e. Yes, it's great

--- He worked out such different questions at a very young age.

--- Oh, he ______ a very smart student then.

A．could have been

B．should have been

C．might have been

D．must have been