副脉

一矩形铜质线框置于如图所示的磁场中，如果把矩形铜质线框从磁场中拉出或进一步推入，下列关于线框所受磁场力的说法中，正确的是

A．拉出时是动力

B．推入时是阻力

C．拉出时不受磁场力

D．推入时不受磁场力

完形填空（共15题，每小题1分，满分15分）

阅读下面短文，掌握大意，然后从短文后各题所给的四个选项（A、B、C和D）中，选出最佳答案，并在答题卡上将该项涂黑。

A long time ago, in a small house in Scotland, two friends lived together. Their names were John and Bobby.

John and Bobby were not  16   , and they had few things except friends,    17    they were happy. They lit a warm fire when it was cold outside. They had food to eat when they were hungry. They were  never     18     because they had each other.

John and Bobby     19     to take long walks together. After their     20     John usually cooked the dinner. John and Bobby ate the dinner and then     21    in front of the fire. They had a(n)     22     but happy life.

Then John developed a(n)     23     disease and died in the spring of 1858. He was  24     in a grave (坟墓). After that, Bobby stood at John’s grave and shouted. “Come on, Bobby,” John’s     25     said. “It’s time to go home.” Bobby went home, but later he returned to the grave. He     26     near it. He stayed there all night.

Bobby stayed at the grave site the next day, and the day after another. For the next 14 years, Bobby never left the    27    . When the weather was cold, he slept in a small house near the grave. When it was     28    , he slept on the ground near John’s grave.

29    , in 1872, Bobby died, too. John’s friends buried him in a     30     grave near John’s. Why was Bobby’s grave so little? Bobby, John’s best friend, was a dog.

16. A. rich                  B. lucky          C. beautiful      D. funny 

17. A. and               B. or         C. but             D. so

18. A. lonely           B. alone         C. worried                D. separate

19. A. failed   B. competed  C. imagined         D. liked

20. A. work           B. rest     C. run                 D. walk

21. A. sang                B. talked          C. sat    D. studied

22. A. hard                 B. sad          C. easy         D. simple

23. A. serious  B. unhealthy   C. big     D. sick

24. A. put                   B. escaped       C. stored         D. buried

25. A. friends B. children  C. parents   D. brothers

26. A. got up    B. turned down         C. sat down D. put up

27. A. garage   B. grave         C. home          D. town

28. A. cool                  B. warm        C. wet                D. rainy

29. A. Luckily    B. Quickly        C. Finally   D. Interestingly

30. A. large     B. small    C. firm     D. weak

便秘的病因。

蒸汽压缩式理论制冷循环的热力完善度是( )。

A．实际制冷循环的制冷系数和相应高低温热源的逆卡诺循环的制冷系数之比
B．实际制冷循环的制冷系数和理论循环的制冷系数的比值
C．理论循环的制冷系数和相应高低温热源的逆卡诺循环的制冷系数之比
D．理论循环的制冷系数和轴功率之比

下列比率中哪个越高，代表企业承担债务的能力越强( )。

A．流动比率
B．现金流动负债比
C．现金到期债务比
D．偿债备付率