抗旱救灾保民生，万众一心破难关——西南五省区市党委、政府领导积极组织指挥抗旱救灾，采取各项有力措施，干方百计保障城乡居民生活用水、春耕生产有序进行、社会秩序稳定、最大限度降低灾害损失。材料说明了     
①***发挥领导核心作用，执政为民②我国政府坚持权为民所用、利为民所谋
③民主执政、科学执政通过依法执政体现和保障④政府能否有权威从根本上是能否走群众路线决定的

所受重力G₁=8N的砝码悬挂在绳PA和PB的结点上．PA偏离竖直方向37°角，PB在水平方向，且连在所受重力为G₂=100N的木块上，木块静止于倾角为37°的斜面上，如图所示，试求：

数列{a_n}中， $a_1=\frac{1}{2}，a_{n+1}=\frac{n{a}_n}{\left(n+1\right)\left(n{a}_n+1\right)}\left(n\in N^{*}\right)$ ，若不等式 $\frac{3}{n^2}+\frac{1}{n}+t{a}_n\ge 0$ 恒成立，则实数t的取值范围是____．

等于（   ）

根据短文内容，选择最佳答案。

    "Everything happens for the best." my mother said whenever things weren't going my way. "Don't worry. One day your luck will change."

    I found mom was right after I finished my college education. I had decided to try for a job in a radio station. I wanted to host a sports program one day. I went to Chicago and knocked at the door of every station. But I got turned down every time.

    In one station, a kind lady said my problem was that I hadn't got enough experience." Get some work in a small station and work your way up," she said.

    I went back home. I couldn't get a job there, either. I felt really down. "Your luck will change," Mom said to me. I tried another radio station in Iowa. But the owner told me he had already had someone. As I left his office, I asked, "How can someone be a sports announcer (播音员) if he can't get a job in a radio station?"

    I was waiting for the lift when I heard the man call. "What did you mean? Do you know anything about football?" He put me in front of a microphone and asked me to try to imagine that I was giving my opinion on a football game, I succeeded.

    On my way home, Mom's words came back to me," One day your luck will change, Son. And when it happens, you'll feel doubly good because of all the hard work you've had." At that moment I knew just what she meant.