We humans live in different parts of the world, but we have the same “mother”. She gives us everything we need in our daily life. She is our Mother Earth.
    April 22 is Earth Day. The theme of this year is “Green Cities”.
    A green city is a healthy and pleasant place for people to live, according to the United Nations.
     A green city can get its energy from renewable (可再生的) sources like solar (太阳能的) and wind power. Also, it is connected by clean public transportation. Moreover, a green city is made up of facilities (设施) that can save energy and reduce waste.
Around the world, many cities and countries have done well to build themselves in a green way.
     Chicago is well known for its green roof (屋顶) program. These roofs are covered with plants. The plants get a great amount of rainwater. Later, the water evaporates (蒸发) to help make the air cool and clean. So far, there are about 360 green roofs in Chicago, according to the US Environmental Protection Agency.
      Curitiba, Brazil, has great transportation. It opened the world's first bus rapid transit (BRT) system in 1974. BRT runs on special lanes. This makes sure that buses are on time even in traffic jams. With the help of BRT, the city has the lowest level of air pollution in Brazil. Today, many other countries have copied BRT, including China and Mexico.
      Singapore is home to the first zero-energy building in Southeast Asia. Zero energy means a building is able to create more energy than it uses. Zero-energy buildings work with solar panels (板) mainly on roofs. These panels can make electricity which powers the buildings. By 2030, Singapore plans to build 80 percent of its buildings like this.

   ①松鼠是一种漂亮的小动物，驯良，乖巧，很讨人喜欢。

   ②它们面容清秀，眼睛闪闪有光，身体矫健，四肢轻快，非常敏捷，非常机警。玲珑的小面孔，衬上一条帽缨形的美丽的尾巴，显得格外漂亮；尾巴老是翘起来，一直翘到头上，身子就躲在尾巴底下歇凉。它们常常直竖着身子坐着，像人们用手一样，用前爪往嘴里送东西吃。可以说，松鼠最不像四足兽了。

   ③松鼠不躲藏在地底下，经常在高处活动，像鸟类似的住在树上，满树林里跑，从这棵树跳到那棵树。它们在树上做窝，摘果实，喝露水，只有树被风刮得太厉害了，才到地上来。在田野里，在平原地区，是找不到松鼠的。它们从来不接近人的住宅，也不呆在小树丛里，只喜欢大的树林，住在高大的树上。在晴明的夏夜，可以听到松鼠在树上跳着叫着，互相追逐的声音。它们好像很怕强烈的日光，白天躲在窝里歇凉，晚上出来练跑，玩耍，吃东西。它们虽然也捕捉鸟雀，却不是肉食兽类，常吃的是杏仁、榛子、榉实和橡栗。

   ④松鼠不敢下水。有人说，松鼠过水的时候，用一块树皮当作船，用自己的尾巴当作帆和舵。松鼠不像山鼠那样一到冬天就蛰伏不动。它们是十分警觉的，只要有人稍微在树根上触动一下，它们就从窝里跑出来，躲在树枝底下，或者逃到别的树上去。松鼠跑跳轻快极了，总是小跳着前进，有时也连蹦带跳。它们的爪子是那样锐利，动作是那样敏捷，一棵很光滑的高树，一忽儿就爬上去了。松鼠的叫声很响亮，比黄鼠狼叫声还要尖些。要是被人家惹恼了，还会发出一种不高兴的恨恨声。

   ⑤松鼠的窝通常搭在树枝分叉的地方，又干净又暖和。它们搭窝的时候，先搬些小木片，错杂着放在一起，再用一些干苔藓编扎起来；然后把苔藓挤紧，踏平，使那建筑物既宽广又坚实，可以带着儿女住在里面，既舒适又安全。窝口朝上，端端正正，很狭窄，勉强可以进出；窝口上有一个圆锥形的盖，把整个窝遮蔽起来，可以使雨水向四周流去，不落在窝里。

请结合上述材料,为促进我国大学生就业提出合理的建议。