“草盛豆苗稀”体现了草和豆苗之间的关系是（   ）

已知函数 $f\left(x\right)=-2x^2+ax+b$ 且 $f\left(2\right)=-3$ ．

根据短文理解完成下列各题。
C
    Tom is a junior high student. He is good at some subjects but his favourite subject is chemistry. Yesterday he met some trouble when he had his chemistry class.
    At that moment, Tom was doing an experiment in class. He tried twenty times, but he couldn't succeed. So he decided to stop doing the experiment. He felt really unhappy.
    His teacher came up to him and asked why he was unhappy. Tom said, "All my work is in vain (白费力气). I fail twenty times and I get nothing."
    Tom's teacher touched Tom's head with a smile. He said to Tom, "Oh, you do a lot and you can get a lot from the mistakes. At least, you know that there are twenty ways you can't use to do this experiment."
    After hearing the teacher's words, Tom became excited. He kept doing the experiment, improved his methods, and he succeeded at last.

数列{a_n}是正项等比数列，{b_n}是等差数列，且a₅=b₄，则有（   ）

我国现阶段的基本国情是社会政治稳定和经济持续快速发展。