购买好火车票的团体旅客，因临时有变退票时，必须在离开车前（）小时前办理，中途站不能退

As a volunteer(自愿者) teacher, I traveled a long way to a small village school in Longzhou, Guangxi. On my way there, I thought about the village, the school and the childrenn there. However, my heart sank when I arrived there. It wasn't what I expected. It didn't look like a school at all! The school had only three rooms, one for Grades 1, 2 and 3, and the other for Grades 4, 5 and 6. There was a third one for me.

　　The children welcomed me warmly on my first day. They asked me a lot of questions, and I told them stories about myself and my life in Shanghai. The next day, I gave them a test to find out their level（水平）. To my surprise, though the test was very easy, over half of the students failed it, yet they all wanted to learn new things. I knew they needed me.

I was busy preparing lessons and reading test papers every night. I enjoyed teaching these lovely and hard-working children, and I could see that they were making progress(进步) with my help. I have also learned a lot from them. I understand their level is becoming higher and higher, and we are good friends now.

I worked in Longzhou for a year. I'm very happy, and the experience(经历) is very useful to me. I love the small village and the children. In fact, I would like to continue working here.

小题1:How many grades are there in the school?

A．2

B．4

C．5

D．6小题2:The writer came from        .

A．Longzhou

B．Guangxi

C．Shanghai

D．Beijing小题3:What does the writer think of working in the school?      .

A．Boring

B．Useful

C．Careful

D．Surprising小题4:According to the passage. The writer        .

A．was sorry for the school

B．worked hard to teach the children

C．don’t want to work in the school

D．left the school in a short time

定量库存控制是指库存量下降到（）时，按固定的订购数量进行订购的方式。

A.订购点 

B.订购批量 

C.安全库存量 

D.最低库存量

已知两个共点力的合力为50 N，分力F1的方向与合力F的方向成30°角，分力F2的大小为30 N。则(　　)

A．的大小是唯一的

B．的方向是唯一的

C．有两个可能的方向

D．可取任意方向

为什么输送机要安装调心托辊？

当泵的填料或机械密封选用或安装不当，可能出现（）。

A、消耗功率过大

B、泵过分发热或转不动

C、流量扬程不足

D、泵输不出液体