PassagetwoExerciseisoneofthefewfactorswithapositiveroleinlong-termmaintenanceofbodyweight.Unfortunately,thatmessagehasnotgottenthroughtotheaverageAmerican,whowouldrathertryswitchingto“light”beerandlow-caloriebreadthanincreasephysicalexertion.TheCentersforDiseaseControl,forexample,foundthatfewerthanone-fourthofoverweightadultswhoweretryingtoshedpoundssaidtheywerecombiningexercisewiththeirdiet.Inrejectingexercise,somepeoplemaybediscouragedtoomuchbycaloric-expenditurecharts:forexample,onewouldhavetobrisklywalkthreemilesjusttoworkoffthe275caloriesinonedeliciousDanishpastry.Evenexerciseprofessionalsconcedehalfapointhere.“Exercisebyitselfisaverytoughwaytoloseweight,”saysYorkOnnen,programdirectorofthePresident’sCouncilonPhysicalFitnessandSports.Still,exercise’ssupportingroleinweightreductionisvital.AstudyattheBostonUniversityMedicalCenterofoverweightpoliceofficersandotherpublicemployeesconfirmedthatthosewhodietedwithoutexerciseregainedalmostalltheiroldweight,whilethosewhoworkedexerciseintotheirdailyroutinemaintainedtheirnewweight.Ifyouhavebeensedentaryanddecidetostartwalkingonemileaday,theaddedexercisecouldburnanextra100caloriesdaily.Inayear’stime,assumingnoincreaseinfoodintake,youcouldlosetenpounds.Byincreasingthedistanceofyourwalksgraduallyandmakingotherdietaryadjustments,youmayloseevenmoreweight.　　6.WhatissaidabouttheaverageAmericaninthepassage?

大信号峰值包络检波器能解调________信号。

28、混凝土强度试验，试件尺寸愈大，强度愈高。（）

24、安全边际是现有或预计的销售业务量与保本点业务量之间的差量，安全边际指标越大越好。

一、选择题2、真空中有两个点电荷，它们之间的静电力为F，若把两个点电荷的电量都增加到原来的2倍，则它们之间的库仑力（）

一、选择题

一、选择题5、一束白光垂直照射在一光栅上，在形成的同一级光栅光谱中，偏离中央明纹最远的是（）

三、判断题2、运动的电荷可以产生磁效应。（）

三、判断题3、静电场是由静止电荷产生，感生电场是由变化的磁场产生。（）

三、判断题4、当光从光密介质正入射于光疏介质时，反射光有半波损失。（）