空分装置短期停车后开车应注意一些什么？请分析说明。

若一个三角形的最大角是最小角的2倍，那么最小角α的取值范围是 36°≤α≤45°．

通过计算和比较技术改造项目的各方案在整个寿命期间内收益的现值与成本比率，以确定各技术改造方案排列的优先次序和取舍的方法是（）。

A.利润分析法

B.效益成本分析法

C.投资回收期法

D.追加投资回收期法

2002年某省文物事业机构数目由上年的158个增加到了164个，文物事业机构人员数由上年的2420人减少到了2393人。具体如下： 文物单位：文物单位个数为63个，比上年增加5%，文物单位人员数为320人，比上年增加7.02%。其中：文物保护管理单位个数为61个，比上年增加5.17%，文物科研及其它文物单位个数为2个，与上年相等：文物保护管理单位人员数266人，比上年增加 9.47%，文物科研及其它单位人员数为54人，比上年减少3.57%。 博物馆：博物馆个数为90个，比上年增加3.45%，博物馆人员数为1690人，比上年减少2.14%。其中：综合类博物馆个数为43个，比上年增加16.22%，历史类博物馆个数为 34个，比上年减少8.11%，艺术类博物馆个数为6个，比上年增加20%，其他博物馆个数为7个，比上年减少12.5%；综合类博物馆的人员数为1004人，比上年增加2.76%，历史类博物馆的人员数为568人，比上年减少11.25%，艺术类博物馆人员数为69人，比上年增加21.05%；其他博物馆人员数为49人，比上年减少7.55%。 文物商店：文物商店个数为11个，与上年相等，文物商店人员数为383人，比上年减少2.79%。

下列说法正确的是（）

A．文物科研及其它文物单位占文物事业机构数目的比例与上年相比没有变化

B．文物单位个数占文物事业机构数目的比例比上年增加了约5个百分点

C．2001年综合类博物馆的数目比历史类博物馆多

D．文物保护管理单位和历史类博物馆的总数与上年相等

用氟离子选择电极法测得某溶液E=290mV，相应的氟离子浓度为2.31mg/L，已知其E-logC的斜率为59mV，测得另一溶液的E=231mV，其相应的氟离子浓度为（）

A.5.9mg/L

B.231mg/L

C.23.1mg/L

D.290mg/L

E.2.31mg/L

There are many kinds of friends. Some are always (1) you, but don’t understand you. Some say only a few words to you, but understand you. Many people will step in your life, but only (2) friends leave footprints.

I shall always recall the autumn and the girl with the (3) . She will always bring back the friendship between us. I know she will always be my best friend.It was the golden season. I could see the yellow leaves (4) with the cool (5) . In such a season, I liked walking alone on the roads covered with leaves, (6) to the sound of them.Autumn is a (7) season and life is uninteresting. The free days always get me (8) . But one day, the sound of a violin (9) into my ears like a stream flowing in the mountains. I was so surprised that I jumped to see what it was. A young girl, standing in the wind, was (10) in playing her violin.

I had (11) seen her before. The music was so nice that I listened quietly. Lost in the music, I didn’t know that I had been (12) there for so long but my existence did not seem to disturb her.Leaves were still falling. Every day she played the violin at the comer of the building (13) I went downstairs to watch her performance. I was the only listener. The autumn seemed no longer lonely and life became (14) . (15) we didn’t know each other, I thought we were already good friends. I believe she also loved me.Autumn was nearly over. One day, when I was listening carefully, the sound suddenly (16) . To my astonishment, the girl came over to me.

"You must like music from the violin." she said."Yes. And you play very well. Why did you stop’." I asked.Suddenly, a (17) expression appeared on her face and I could feel something unusual."I came here to see my grandmother, but now I must leave. I once played very badly. It was your listening every day that (18) me. " she said."In fact, it was your playing (19) gave me a meaningful autumn," I answered, " Let’s be friends. "The girl smiled, and so did I. I never heard her play again in my life. I no longer went downstairs to listen to her. Only thick leaves were left behind. But I will always remember the fine figure of the girl. She is like a (20) —so short, so bright, like a shooting star giving off so much light that makes the autumn beautiful.

第（5）空应选择（）

A.wind 

B.snow 

C.air 

D.rain