命题“$\exists x\in R$,使得$x^2+x+1<0$”的否定是 (   )

若x=﹣2是函数f（x）=（x²+ax﹣1）e^x﹣1的极值点，则f（x）的极小值为（    ）

“山歌越唱越开怀，东山唱到西山来。湘赣边工农革命损失大，井冈山找对革命路径来。”民歌中“井冈山找对革命路径”的准确含义是（  ）

A

    Most Americans start to school at the age of five when they enter kindergarten(幼儿园). Children do not really study at this time. They only attend for half the day and learn what school is like. Children attend elementary school for the next six years. They learn to read and write and work with numbers. They also study the world and its people. After they leave elementary school, children go to junior high school for three years and senior high school for another three years. This is called secondary education. In some places, the children go to elementary school for eight years and high school for four. In all, elementary and secondary education together take twelve years to complete excluding （不包括）kindergarten.

根据短文，选择最恰当的选项。