—What’s wrong with you? —_______________

阅读理解。

      John was ten years old and he was very lazy. He had to go to school, of

course, but he was bored there and tried to do as little work as possible. His father and mother were

both doctors and they hoped that he would become one, too, when he grew up. But one day John

said to his mother, "When I finish school, I want to become a garbage collector."

     "A garbage collector?" his mother asked .She was very surprised. "That's not

a pleasant job. Why do you want to become a garbage collector?"

     "Because then I'd only have to work one day a week," John answered.

     "Only one day a week?" his mother said, "What do you mean?"

     "Well," John answered, "I know that the ones who come to our house only

work on Wednesday, because I only saw them on that day."

1. John_____at school.

A. didn't do any work

B. did much work

C. did very little work  

D. tried to finish his work   

2. John's parents wanted him to become______.    

A. a garbage collector  

B. a doctor

C. a teacher          

D. a worker  

3. John hoped to be a garbage collector because______.    

A. he knew it was an important and necessary job

B. he thought he would work only one day a week

C. he often saw some garbage collectors come to his house

D. the garbage collectors really work only one day a week 

4. John thought that the garbage collectors only work one day a week because ______.

A. it was a rule              

B. some garbage collectors told him so

C. his parents told him so      

D. he saw them work only on Wednesday

某同学利用甲基绿对人的口腔上皮细胞进行染色处理，若操作正确，则被染成绿色的结构是[ ]

A．细胞膜

B．细胞质

C．细胞核

D．核糖体

“劣币驱逐良币”现象存在于（）。

A.银元本位制

B.银两本位制

C.平行本位制

D.双本位制

配制混凝土时对集料有严格要求，若混凝土用砂中的硫化物和硫酸盐含量较高，会影响混凝土的（）性能。

A．影响混凝土强度和耐久性

B．对水泥有侵蚀作用

C．影响水泥的凝结与硬化、强度与耐久性

D．导致钢筋锈蚀

管道系统的清洗目的是什么？