如图所示是研究DNA复制方式的实验，根据这些实验结果进行的推论，正确的是（　　）

①丙是转入¹⁴N培养基中复制一代的结果   

②乙是转入¹⁴N培养基中复制二代的结果

③出现丁的结果至少需要60分钟         

④戊图表示复制三代后不再具有¹⁵N标记DNA．

补全对话。

A. She is a doctor. 

B. How does she go to work?

C. What does your father do?

D. I want to be a pilot. 

E. Do you want to be a pilot, too? 

Bill: Hi! Mike! ____       

Mike: He is a scientist.  

Bill: Does he like his job?           

Mike: Yes, but he's very busy.

Bill: What about your mother?      

Mike: ____ 

Bill: Oh, doctors always work hard.  

Mike: Yes, but it is interesting. 

Bill: ____                

Mike: She goes to work by bus. 

Bill: What are you going to do when you grow up (长大)? 

Mike: ____

Bill: It's cool.      

Mike: ____   

Bill: No, I want to be a writer.