过原点且倾斜角为的直线被圆所截得的弦长为

A．           B．            C．             D．

函数的定义域是

    A． B．    C． D．                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         

命题“存在，使得”的否定是

A．不存在，使得         B．存在，使得

C．对任意，都有           D．对任意，使得

已知全集,，则

A．            B．          C．         D．

已知函数．

（Ⅰ）若函数在上为增函数，求实数的取值范围；

（Ⅱ）当且时，证明： . 

已知椭圆：的左、右焦点分别为、，椭圆上的点满足，且△的面积为．

（Ⅰ）求椭圆的方程；

（Ⅱ）设椭圆的左、右顶点分别为、，过点的动直线与椭圆相交于、两点，直线与直线的交点为，证明：点总在直线上.

已知数列的前项和为，且．

（Ⅰ）求数列的通项公式；

（Ⅱ）设，，

求使恒成立的实数的取值范围．

设，函数满足．

（Ⅰ）求的单调递减区间；

（Ⅱ）设锐角△的内角、、所对的边分别为、、，

且， 求的取值范围．

为了参加2013年市级高中篮球比赛，该市的某区决定从四所高中学校选出人组成男子篮球队代表所在区参赛，队员来源人数如下表：

该区篮球队经过奋力拼搏获得冠军,现要从中选出两名队员代表冠军队发言．

（Ⅰ）求这两名队员来自同一学校的概率；

（Ⅱ）设选出的两名队员中来自学校甲的人数为，求随机变量的分布列及数学期望．

已知函数.

（Ⅰ）若，求函数的单调区间和极值；

（Ⅱ）设函数图象上任意一点的切线的斜率为，当的最小值为1时，求此时切线的方程.