已知数列$\left\{a_n\right\}$的a₁=1，且$\frac{a_{n+1}}{a_n}=1-n{a}_{n+1}$，则此数列$\left\{a_n\right\}$的通项公式为（    ）

    Recently I read the Human Development Report. I couldn't help thinking about another problem which the world is facing--hunger. According to the report, 2,400 people are dying from hunger every day; nearly 13 million in southern Africa will be worried about their food supply because of earthquakes, floods or wars.

    In a word, hunger remains the biggest problem of the world today. It's strange to see that man can travel to the moon, but still doesn't know how to feed himself. You may ask, “Who steals our bread? The first thieves should be population growth, poverty and loss of rich farmland.

    In less developed areas like South Africa, the population grows faster than the crops. It is almost impossible for its government to feed so many people and provide education for them. So it is very important to control the population growth and protect their farmland in countries whose people are suffering from hunger.

    According to the report, the world's food production is enough to feed everyone if it is given away well. But the problem is that the developed countries are eating food that should be given to the poor. Although they are just using their own earning, the fact is that they are coldly watching others starving away.

    Luckily, some developed countries such as Netherlands, Norway and Sweden have done a lot to help those hungry people in African countries. We hope other developed countries will follow them.

补写出下列句子中的空缺部分。

①在《生于忧患，死于安乐》中，孟子认为上天要让一个人担负重大使命，一定会让这个人经历种种艰难困苦，最终“____，____”。

②人们常说：“活到老，学到老。”荀子《劝学》篇中的“____”一句充分印证了这句话。

③李白在《蜀道难》一诗中先用“____，____”托出山势的高险，然后通过描写急流、瀑布发出巨大声响来写其险。