B

　　The human body naturally prevents attempt( 企 图 )to lose or gain　　weight.Thus the best way to lower your weight is to do some exercise　daily.Although scientists don’t agree exactly　how this works to lower the“setpoint”，they do know that exercise　helps your body work with you and not against you in at least the

　　following ways：

　　1.Exercise burns calories(卡路里)：if you walk two miles every day，　you use an extra 1400 calories a week—and lose about a pound in two　weeks.

　　2.Exercise helps to bum fat and build muscle：since muscle requires　more calories than fat does，the more muscle you have，the faster you　will bum calories.

　　3.Finally exercise speeds up your metabolism(新陈代谢)，not just　while you’re exercising，but for several hours after exercise ends.

　　A program of light-to-moderate exercise done for only a half-hour a　day is enough to keep your“setpoint”lowered，and thus helps you lose　　weight and keep it off.If you need to lose more than five pounds ，combine regular exercise with a moderate reduction in calories until you　reach your goal(目标).

　　40.Scientists don’t________.

　　A.think exercise helps people's bodies work against them

　　B.agree exercise helps to lower people's weight

　　C.bilieve in exercise at all

　　D.think exercise helps people's bodies work with them

　　答案：A

　　41.Exercise helps you________.

　　A.save calories and gain weight

　　B.save calories but lose weight

　　C.bum calories and lose weight

　　D.burn calories but gain weight

　　答案：C

　　42.When you walk________.

　　A.slowly，the fat in your body increases

　　B.1ess，you build more muscles

　　C.faster，you bum less calories

　　D.fast，the fat in your body reduces

　　答案：D

　　43.Which of the following is NOT true?

　　A.A man of more muscles burns calories faster.B.Exercise speeds up your metabolism even after it.

　　C.An hour and a halls exercise is not enough to keep your“setpoint”　　lowered.

　　D.To lose more than 5 pounds，just doing exercise is not enough.

　　答案：C