单选题函数的连续区间是()。

单选题如图60所示，M为平行四边形ABCD的AB边上的中点，AC交MD于点E，则图中阴影部分的面积与平行四边形ABCD面积的比是()．

单选题若直线y=x+b与曲线恰有一个公共点，则b的取值范围是______．A．(-1，1]或B．(-1，1]或C．(-1，1)或D．E．以上答案均不正确

单选题设，则当x=0时，一定是无穷小量的是()．

单选题设a、b、c为整数，且|a-b| 20 +|c-a| 41 =1，则|a-b|+|a-c|+|b-c|=______．

单选题用待定系数法求微分方程y"-y=xe x 的一个特解时，特解的形式是(式中a、b是常数)______．

单选题设A是4阶矩阵，若α1=(1，0，-1，1)T，α2=(0，1，-1，0)T，α3=(1，1，0，1)T是非齐次线性方程组Ax=b的三个解，A*为A的伴随矩阵，则下列各命题中不正确的是( )

单选题若f(x)的一个原函数是e-x，则不定积分∫xf(x)dx等于 A.e-x(x+1)+C B.e-x(1-x)+C C.e-x(x-1)+C D.-e-x(x+1)+C

单选题如图10—2，设罪犯与警察在一开阔地上相隔一条宽0．5公里的河，罪犯从北岸A点处以每分钟1公里的速度向正北逃窜，警察从南岸B点以每分钟2公里的速度向正东追击．则警察从B点到达最佳射击位置(即罪犯与警察相距最近的位置)所需的时间是()．

单选题设{a n }是等比数列，S n 是它的前n项和，若S n =10，S 2n =30，则S 6n -S 5n 等于( )．

单选题设f(x)在x=0处可导，，则f′(0)=()．

单选题设为连续函数，则a等于______

单选题____A．1B．cos1C．0D．

单选题 分别是数域上的维线性空间，则由全体双线性型组成的线性空间的维数是 A、 B、 C、 D、

单选题接种某疫苗后，出现发热反应的概率为0.80．现有5人接种该疫苗，至少有3人出现发热反应的概率为(精确到0.01)______

单选题在由1、2、3、4、5构成的各位数字不同的三位数中，任取一个恰是偶数的概率为{{U}}{{/U}}。A．B．C．D．

单选题等于____。A．0B．C．2D．1

单选题Arsenic, a naturally occurring poison and carcinogen found in ground water, is strongly linked to adult-onset diabetes, U. S. researchers said on Tuesday. Odorless, tasteless, colorless and easily soluble in water or wine, arsenic has long been a feared poison. A heavy dose is detectable in a corpse, but researchers say small amounts of arsenic may sicken people gradually. Dr. Ana Navas-Aeien and colleagues at Johns Hopkins University in Baltimore found a " relatively strong " association between commonly found levels of arsenic in urine and type 2 diabetes in a study of American adults. " It seems there is maybe no safe level of arsenic. " Navas-Acien said in a telephone interview. " Worldwide it's a huge problem, " she said. " As water becomes a scarce resource. the situation becomes even more serious. " Arsenic raises the risk for cancers of the bladder, lung, kidney, skin and, possibly, the pros tate, Navas-Acien said. The 20 percent of nearly 800 study participants who had the most arsenic in their bodies, a tolerable 16. 5 micrograms per liter of urine, had 3. 6 times the risk of developing late-onset diabetes than those in the bottom 20 percent, who had 3 micrograms per liter. Levels of arsenic were 26 percent higher in people with late-onset, or type 2, diabetes than those without the disease, the study found. The U. S. government sets a limit for drinking water at 10 micrograms of arsenic per liter, which is exceeded in the water consumed by 13 million Americans who mostly live in rural areas that rely on wells to bring up ground water, the researchers wrote in the Journal of the American Medical Association. Arsenic contaminates drinking water for millions of people in Bangladesh, parts of Central Europe, Chile, Argentina and the western United States, where ground water is the source of drinking water and the land has higher concentrations of arsenic. Overall, 7. 8 percent of Americans are believed to have diabetes, although some do not know it. At least 90 percent of cases are the type 2 variety, in which the body loses its ability to use insulin properly. Navas-Acien said arsenic may play a significant role in diabetes incidence, but it is difficult to say how much. Arsenic can accumulate in the body, and can ruin the body's ability to use insulin and perform the vital task of converting blood sugar into energy. Normally, insulin fits into cells via molecular doorways called receptors, which in turn signal the cell to move glucose inside, but arsenic enters the cell and somehow blocks the activity. Seafood is another source of arsenic, but the organic form found in shellfish and some fish has a carbon molecule attached and poses no risk to health, she said.

单选题Aboxcontains100balls,numberedfrom1to100.Ifthreeballsareselectedatrandomandwithreplacementfromthebox,whatistheprobabilitythatthesumofthethreenumbersontheballsselectedfromtheboxwillbeodd?

单选题设函数f(x)连续，，其中区域Duv为图中阴影部分，则______．A．vf(u2)B．C．vf(u)D．