单选题曲线

单选题The idea that some groups of people may be more intelligent than others is one of those hypotheses that dare not speak its name. But Gregory Cochran is (1) to say it anyway. He is that (2) bird, a scientist who works independently (3) any institution. He helped popularize the idea that some diseases not (4) thought to have a bacterial cause were actually infections, which aroused much controversy when it was first suggested. (5) he, however, might tremble at the (6) of what he is about to do. Together with another two scientists, he is publishing a paper which not only (7) that one group of humanity is more intelligent than the others, but explains the process that has brought this about. The group in (8) are a particular people originated from central Europe. The process is natural selection. This group generally do well in IQ test, (9) 12-15 points above the (10) value of 100, and have contributed (11) to the intellectual and cultural life of the West, as the (12) of their elites, including several world-renowned scientists, (13) . They also suffer more often than most people from a number of nasty genetic diseases, such as breast cancer. These facts, (14) , have previously been thought unrelated. The former has been (15) to social effects, such as a strong tradition of (16) education. The latter was seen as a (an) (17) of genetic isolation. Dr. Cochran suggests that the intelligence and diseases are intimately (18) . His argument is that the unusual history of these people has (19) them to unique evolutionary pressures that have resulted in this (20) state of affairs.

单选题若[x]表示不超过x的最大整数，则积分的值为______

单选题设积分区域D={(X，y)||x|+|y|≤1)，则二重积分的值等于A．1．B．C．2．D．

单选题已知A=(aij)n×n，B=(bij)n×n且有关系(i，j=1，2，…，n)，则下列关系式正确的是______。A．A(B+E)=BB．(B+E)A=BC．B(A-E)=AD．(E-A)B=A

单选题设，则

单选题设则当x→0时，f(x)与g(x)相比是______

单选题设二元函数f(u，v)对任何(u，v)具有一阶连续偏导数，且f(0，0)=0，f'u(u，v)f'v(u，v)≠0，则对任何(x，y)，下列等式恒成立的是

单选题下述极限不正确的是A．．B．．C．．D．．

单选题在下列命题中正确的是A．若都收敛，则收敛．B．若收敛，发散，则发散．C．若条件收敛，绝对收敛，则条件收敛．D．若收敛，绝对收敛，则绝对收敛．