职称英语在线答题

每日一练：职称英语考试理工类每日一练(2017/11/17)
【单选题】

All of US have felt pain.We have cutourselves.We have been burned.Or we have had headaches.Some of us suffer painrarely pain rarely. (46)

Pain can take complete control of our body andmind，making it impossible to move and even to think.Yetwe need pain.Without it，we would not know.1f we havehurt ourselves.It is our body’s warning system. (47)

Pain is the most common reason we go to adoctor It is the most common reason we take medicines.Until recently，however, most doctors knew of only a few drugs that stopped somepains (48)But new knowledge about the process of pain is helping them tocontrol pain better.

Scientists have learned that the sense of painis made up of both chemical and electrical signals. (49)Scientists also havelearned that the nervous system sends two different kinds of pain messages tothe brain：one very fast，theother slow.The first message is the warning signal.It moves at a speed of 30meters a second.In less than a second，the brainunderstands that part of the body is hurt and how badly it is injured. (50)Ittells us not to use the injured part until it heals.

A And others have painful attacks all the time.

B These signals travel from nerve cells in theinjured area，up the spinal cord(脊髓)to the brain，and back down again.

C It tells us that We are injured and should dosomething about it

D They knew little about the process of painitself.

E The other message moves at a speed of only013~meter a second.

F And they send the second，slower message of pain to the brain.