某操作系统采用段式管理，用户区主存为512KB，空闲块链入空块表，分配时截取空块的前

心的正常起搏点是

A．窦房结

B．房室结

C．房室束

D．浦肯野纤维

E．左、右束支

选择适当的句子补全对话（其中有一个多余选项）。

A: Hi, Lisa! Nice to meet you again.

B: Hi, Cindy. 1. _____

A: I usually get up at 6:30. 2. _____

B: At 5:30.

A: Really? 3. _____

B: Yes, first I run then I do morning

A: Do you go to school by bus?

B: 4. _____

A: Oh, you have a good habit .(习惯).

B: Thank you. That's because 5. _____

A  I 1ike sports very much.

B. What time do you go to school?

C. When do you usually get up?

D. No, I walk to school.

E.  How about you?

保管、使用增感屏的方法中，错误的是（）

A.防高温、防潮湿

B.防阳光暴晒

C.防止水或药液溅入

D.发现灰尘可用口吹清除

E.暗盒应直立放置，避免重压变形

聚合反应器开车置换时水氧含量必须小于（）PPm。

A.1

B.2

C.0.2

D.0.5