单选题设向量组α1，α2，…，αs的秩为r1，向量组β1，β2，…，βt的秩为r2，且向量组α1，α2，…，αs可由向量组β1，β2，…，βt线性表出，则

单选题设u=φ(x)在(a，b)可微，则φ(x)=C1x+C2(c1，c2为常数)是du=△u的(A)充分而不必要条件．(B)必要而不充分条件．(C)充要条件．(D)既不充分也不必要条件．

单选题Attempts to understand the relationship between social behavior and health have their origin in history. Dubos (1969) suggested that primitive humans were closer to the animals (1) they, too, relied'upon their instincts to stay healthy. Yet some primitive humans (2) a cause and effect relationship between doing certain things and alleviating (3) of a disease or (4) the condition of a wound. (5) there was so much that primitive humans did not (6) the functioning of the body, magic became an integral component ofthe beliefs about the causes and cures of heath (7) Therefore it is not (8) that early humans thought that illness was caused (9) evil spirit. Primitive medicines made from vegetables or animals were invariably used in combination with some form of ritual to (10) harmful spirit from a diseased body. One of the. earliest (11) in the Western world to formulate principles of health care based upon rational thought and (12) of supernatural phenomena is found in the work of the Greek physician Hippocrates. The writing (13) to him has provided a number of principles underiying modern medical practice. One of his most famous (14) , the Hippocratic Oath, is the foundation of contemporary medical ethics. Hippocrates also argued that medical knowledge should be derived from a (15) of the natural science and the logic of cause and effect relationships. In this (16) thesis, On Air, Water, and Places, Hippocrates pointed out that human well-being is (17) by the totality of environmental (18) : living habits or lifestyle, climate, geography of the land, and the quality of air, and food. (19) enough, concerns about our health and the quality of air, water, and places are (20) very much written in twentieth century.

单选题设A是m×n矩阵，r

单选题设X～N(2，22)，Y=aX+b～N(0，1)，则a，b的可能取值为( )．

单选题设f(x)=|x|，g(x)=x 2 -x，则等式f[g(x)]=g[f(x)]成立时，x的变化范围是______

单选题设f(x)=x2tanx，当x→∞时是

单选题设随机变量X服从正态分布N(μ，σ2)，其分布函数为F(x)，随机变量Y=F(X)，则的值______。A.与参数μ和σ有关B.与参数μ有关，但与σ无关C.与参数σ有关，但与μ无关D.与参数μ和σ均无关

单选题下列命题中正确的是______A．设正项级数发散，则B．设级数收敛，则级数收敛C．设至少有一个发散，则发散D．设收敛，则都收敛

单选题设A为m×n矩阵，r(A)=m，且方程组Ax=0只有零解，则下列结论正确的是(A)方程组有唯一解．(B)m≠n．(C)A的列向量组线性相关．(D)以上都不对．

单选题设f(x)为单调可微函数，g(x)与f(x)互为反函数，且f(2)=4，f"(2)=，f"(4)=6，则g"(4)等于______．A．B．C．D．4

单选题函数y=f(x)在(0，+∞)内有界且可导，则______A．当f(x)=0时，必有f'(x)=0．B．当f'(x)存在时，必有f'(x)=0．C．当f(x)=0时，必有f'(x)=0．D．当f'(x)存在时，必有f'(x)=0．

单选题设总体X服从正态分布N(0，σ2)，X1，…，Xn是取自总体X的简单随机样本，其均值、方差分别为，S2．则A．B．C．D．