函数y=3x-4中自变量x的取值范围是______，函数y=3x-9中自变量x的

要使某一生态系统长期存在，除了非生物部分外，必须具有（　　）

A．消费者和生产者

B．生产者和消费者

C．生产者和分解者

D．生产者和人

在海拔3000m以上的高原地区，汽车发动机的冷却水容易沸腾，这是因为高原地区_________的缘故。常年生活在平原地区的入到达该地区后，由于空气稀薄会产生缺氧反应，为了得到足够的氧气，人会不自觉地进行深呼吸，这时肺的容积与在平原上相比要扩张得更________（选填“大”或“小”）

完形填空(共20小题；每小题1.5分，满分30分)

阅读下面短文，掌握其大意，然后从21~40各题所给的四个选项(A、B、C和D)中，选出最佳选项，并在答题纸上将该选项标号涂黑。

The books in David’s schoolbag felt like bricks as he ran down the street.What he wanted to do was to play basketball with Eric.   21   his mother told him he would have to return his sister’s books to the library first.

He had   22   set foot in a library and he wasn’t about to do so today.He would just  23  

the books in the outside return box.But there was a   24  ;it was locked.

He went into the building,only a few minutes   25   closing time.He put the books into the return box.And after a brief   26   in the toilet,he would be on his way to the playground to   27   Eric.

David stepped out of the toilet and stopped in   28  —the library lights were off.The place was   29  .The doors had been shut.They   30   be opened from the inside.He was trapped(被困)—in a library!

He tried to   31   a telephone call,but was unable to   32  .What’s worse,the pay phones were on the outside of the building.  33    the sun began to set,he searched for a light and found it.

   34   he could see.David wrote on a piece of paper:“    35   !I’m TRAPPED inside!”and stuck it to the glass door.   36  ,someone passing by would see it.

He was surprised to discover that this place was not so unpleasant,   37  .Rows and rows of shelves held books,videos and music.He saw a book about Michael Jordan and took it off the shelf.He settled into a chair and started to   38  .

He knew he had to   39  ,but now,that didn’t seem to be such a   40   thing.

21.A.but                       B.because                     C.or                             D.since

22.A.ever                            B.nearly                       C.never                        D.often

23.A.pass                            B.drop                         C.carry                        D.take

24.A.problem               B.mistake                     C.case                          D.question

25.A.during                  B.after                         C.over                          D.before

26.A.rest                      B.break                        C.walk                         D.stop

27.A.visit                            B.meet                         C.catch                         D.greet

28.A.delight                 B.anger                        C.surprise                     D.eagerness

29.A.lonely                  B.empty                       C.noisy                        D.crowded

30.A.wouldn’t                     B.shouldn’t                   C.couldn’t                    D.needn’t

31.A.make                    B.fix                            C.use                           D.pick

32.A.get on                  B.get up                       C.get through                D.get in

33.A.If                         B.As                            C.Though                     D.Until

34.A.On time                                                   B.Now and then

C.By the way                                                  D.At last

35.A.Come                   B.Help                         C.Hello                        D.Sorry

36.A.Surely                  B.Thankfully                C.Truly                        D.Gradually

37.A.at most                 B.after all                            C.in short                            D.as usual

38.A.watch                   B.play                          C.read                          D.write

39.A.wait                            B.stand                         C.sleep                         D.work

40.A.bad                     B.cool                          C.strange                      D.nice

有关模板、拱架和支架的拆卸的质量控制要点有（）。

A.不承重的侧模板，应在混凝土强度能保证混凝土表面及棱角不致损坏的情况下方可拆除，一般在混凝土抗压强度达到2.5MPa时方可拆除侧模

B.一般跨径不超过4m的梁和板应达到混凝土设计强度等级的50%；跨径超过4m的梁、板应达到混凝土设计强度等级的75%时，方可拆除

C.抽拔芯模的时间，以混凝土抗压强度达到0.4MPa～0.8MPa为宜

D.石块或混凝土预制块拱桥，须待砂浆强度达到图样要求时才能卸架；如图样无规定，一般须达到砂浆设计强度等级的75%

E.跨径小于10m的拱桥，在拱上建筑完成后卸架；中等跨径的实腹式拱，在护拱完成后卸架；中等跨径的空腹式拱，在拱上建筑立墙完成后卸架。裸拱卸架需事先进行验算

下列说法不正确的是（）

A.内环境稳态是机体进行正常生命活动的必要条件

B.调节机体活动的最高级中枢在脊髓

C.人体的细胞外液主要包括血液、组织液和淋巴

D.不同人的体温，因年龄、性别等的不同存在微小的差异