单选题In the United States, the first day-nursery was opened in 1854. Nurseries were established in various areas during the (1) half of the 19th century; most of (2) were charitable. Both in Europe and in the U. S. , the day nursery movement received great (3) during the First World War, when (4) of manpower caused the industrial employment unprecedented numbers of women. In some European countries nurseries were established (5) in munitions plants, under direct government sponsorship. (6) the number of nurseries in the U. S. also rose (7) , this rise was accomplished without government aid of any kind. During the years following the First World War, (8) , Federal, State, and local governments gradually began to exercise a measure of control (9) the day-nurseries, chiefly by (10) them and by inspecting and regulating the conditions within the nurseries. The (11) of the Second World War was quickly followed by an increase in the number of day-nurseries in almost all countries, as women were (12) called upon to replace men in the factories. On this (13) the U.S. government immediately came to the support of the nursery schools, (14) $ 6,000,000 in July, 1942, for a nursery school program for the children of working mothers. Many States and local communities (15) this Federal aid. By the end of the war, in August, 1945, more than 100,000 children were being cared (16) in day-care centers receiving Federal (17) . Soon afterward, the Federal government (18) cut down its expenditures for this purpose and later (19) them, causing a sharp drop in the number of nursery schools in operation. However, the expectation that most employed mothers would leave their (20) at the end of the war was only partly fulfilled.

单选题已知P-1AP=B，若Aα=λα，α=0，则______．A．B的特征值为λ，对应的特征向量是PαB．B的特征值为，对应的特征向量是PαC．B的特征值为λ，对应的特征向量是P-1αD．B的特征值为，对应的特征向量是P-1α

单选题设’其中f(x)在x=0处连续，且f(0)=0．若F(x)在x=0处连续，则k等于______．A．B．0C．D．

单选题设A是m×n矩阵，C是n阶可逆矩阵，矩阵A的秩为r，矩阵B=AC的秩为r1，则______

单选题设A为n阶实矩阵，A T 是A的转置矩阵，对于线性方程组(Ⅰ)：Ax=0和(Ⅱ)：A T Ax=0必有______

单选题在下列四个选项中，正确的是(A)设f'(x0)存在，则(B)设存在．(D)设f(x，y)在点(x0，y0)某邻域内有偏导数，则f(x，y)在点(x0，y0)处连续．

单选题设f(x)为二阶可导的奇函数，且x＜0时有f"(x)＞0，f"(z)＜0，则当x＞0时有______.

单选题设f'(x0)=0，f"(x0)＞0，则必定存在一个正数δ，使得______． A．曲线y=f(x)在(x0-δ，x0+δ)内单调增加 B．曲线y=f(x)在(x0-δ，x0+δ)内单调减少 C．曲线y=f(x)在(x0-δ，x0]内单调减少，而在[x0，x0+δ)内单调增加 D．曲线y=f(x)在(x0-δ，x0]内单调增加，而在[x0，x0+δ)内单调减少

单选题设函数y=y(x)由方程x3-ax2y2+by3=0所确定，要使x=1是y=y(x)的驻点，且曲线y=y(x)通过点(1，1)，则______．A．a=2，b=3B．C．D．a=-2，b=-3