如图所示长木板A放在光滑的水平地面上，物体B以水平速度冲上A后，由于摩擦力作用，

阅读下面短文，掌握其大意，从每题所给的A、B、C、D四个选项中，选出最佳选项，并在答题卡上讲该项涂黑。

A Race Against Death

It was a cold January in 1925 in North Alaska. The town was cut off from the rest of the world due to heavy snow.

On the 20th of that month, Dr.Welch   36   a Sick boy, Billy, and knew he had diphtheria, a deadly infectious(传染的)disease mainly affecting children. The children of Nome would be  37  if it struck the town. Dr.Welch needed medicine as soon as possible to stop other kids from getting sick.   38  , the closest supply was over 1,000 miles away, in Anchorage.

How could the medicine get to Nome? The town`s  39  was already full of ice, so it couldn`t come by ship. Cars and horses couldn`t travel on the   40  roads. Jet airplanes and big trucks didn`t exist yet.

41  January 26, Billy and three other children had died. Twemty more were   42  . Nome`s town officials came up with a(n)  43  . They would have the medicine sent by   44  from Anchorage to Nenana. From there, dogeled(狗拉雪橇)drivers—known as “mushers”—would   45  it to Nome in a relay(接力).

The race began on January 27. The first musher, Shannon, picked up the medicine from the train at Nenana and rode all night.  46  he handed the medicine to the next musher, Shannon`s face was black from the extreme cold.

On January 31， a musher named Seppala had to   47  a frozen body of water called Norton Sound .It was the most  48  part of the journey. Norton Sound was covered with ice,which could sometimes break up without warning.If that happened,Seppala might fall into the icy water below.He would  49  ,and so would the sick children of  Nome.But  Seppala made it across.

A huge snowstorm hit on February 1.Amusher  named Kaasen had to brave this storm.At one point,huge piles of sonw blocked his 50  .He had to leave the trail (雪橇痕迹)to get around them.Conditions were so bad that it was impossible for him to  51  the trail again. The only hope was Balto,Kaasen’s lead dog, Balto put his nose to the ground, 5 2  to find the smell of other dogs that had traveled on the trail.If  Balto failed,it would mean disaster for Nome.The minutes passed by.Suddenly, Balto began to  53  .He had foung the trail

At 5:30 am on February 2, Kaasen and his dog  54  in Nome. Within minutes,Dr.Welch had the medicine.He quickly gave it to the sick children.All of them recoverd.

Nome had been  55  .

37（）

A.harmless

B.helpless

C.fearless

D.careless

消费者行为研究的意义。

“盲样”检验应注意的是，只有在具体分析操作人员完全不知沙样中有检验样品的情况下，运用与平常（）的操作分析，才能使检验样品的分析质量符合常规分析的实际，否则失去“盲样”检验的意义。

A.改进

B.不同

C.类似

D.一样

风险管理的具体目标有（）

A.损失前目标和损失后目标

B.损失中目标

C.损失前目标

D.损失后目标

最易出现水冲脉的是（）

A.二尖瓣狭窄

B.二尖瓣关闭不全

C.主动脉瓣狭窄

D.主动脉瓣关闭不全

E.缩窄性心包炎