单选题In the country we are {{U}}excluded{{/U}} from the worries of life in a big town. A. enveloped B. protected C. insulated D. subtracted

单选题若，则直线y=kx+(m+n)一定经过第______象限．

单选题已知a，b为非零实数，且a＜b，则下列命题成立的是______A．a2＜b2B．a2b＜ab2C．D．E．

单选题在[e，e2]上的最大值为______．A．0B．1C．2ln2D．

单选题O是平面上一定点，A、B、C是平面上不共线的三个点，满足，λ∈[0，+∞)，则P的轨迹一定通过△ABC的______。A．外心B．内心C．重心D．垂心

单选题None of students in the class likes the mistress, who is used to being ______ of everything they do. A. emotional B. optimistic C. interested D. critical

单选题设a＞b＞0，k＞0，则下列不等式中能够成立的是______．A．B．C．D．E．以上结论均不成立

单选题That battered old bat of his is a ______ joke to all his friends. A. steady B. standing C. persisting D. stable

单选题10件产品中有3件是不合格品，今从中任取两件，则两件中至少有一件合格品的概率为______．A．B．C．D．E．

单选题A，B两地相距15千米，甲中午12时从A地出发，步行前往B地，20分钟后乙从B地出发骑车前往A地，到达A地后乙停留40分钟后骑车从原路返回，结果甲、乙同时到达B地，若乙骑车比甲步行每小时快10千米，则两人同时到达B地的时间是______．

单选题设A是3阶不可逆矩阵，E是8阶单位矩阵，若线性齐次方程组(A-3E)x=0的基础解系由两个线性无关的解向量构成，则行列式|A+E|=______

单选题设{an}是等差数列，{bn}是各项均为正数的等比数列，且a1=b1=1，a3+b3=9，a5+b5=25，则______．A．B．C．D．E．

单选题已知关于x的一元二次方程8x2+(m+1)x+m-7=0有两个负数根，那么实数m的取值范围是( )。 A．m＞7 B．m＜7 C．m＞1 D．m＜1

单选题 Observe the dilemma of the fungus: it is a plant, but it possesses no chlorophyl. While all other plants put the sun's energy to work for them combining the nutrients of ground and air into body structure, the chlorophylless fungus must look elsewhere for an energy supply. It finds it in those other plants which, having received their energy free from the sun, relinquish it at some point in their cycle either to other animals (like us humans) or to fungi. In this search for energy the fungus has become the earth's major source of rot and decay. Wherever you see mold forming on a piece of bread, or a pile of leaves turning to compost, or a blown-down tree becoming pulp on the ground, you are watching a fungus eating. Without fungus action the earth would be piled high with the dead plant life of past centuries. In fact, certain plants which contain resins that are toxic to fungi will last indefinitely. Specimens of the redwood, for instance, can still be found resting on the forest floor centuries after having been blown down.