①青草丛中隐藏着一条倾斜的隧道。____

②即使有骤雨，这里也立刻会干的。____

③那微斜的门口，经过仔细耙扫，收拾得很平坦。这就是蟋蟀的平台。____

④屋子的内部没什么布置，但是墙壁很光滑。____

⑤住所是很简朴的，清洁、干燥，很卫生。____

为了保护草原生态系统，我国于1985年颁布了《草原法》．草场的不合理利用，一般表现在（　　）

    Spring is coming．People in different countries like different outdoor activities．Leo，a reporter from Learning English in interviewing（采访）some students．Here is what they have said．
    Mary （13, America）　　
    I want to go out of the city to a beautiful field. It's happy to smell beautiful flowers, touch green grass and take some photos. And I like to have a picnic in the field, It's interesting!
    Jim （14, Canada）　　
    The weather turns warmer and they days become longer in spring. It's a good time to go camping. It would be fun to sleep in a tent. I enjoy the comfortable weather too.
    Tony （13, England）
    In spring, I like going cycling alone. It can not only make me enjoy the beautiful season but also help me became stronger. I can write something about what I see on the way.
    Wang Fang （12, China）
    I'm good at making all kinds of kites. And in spring. I like flying kites with my family or my friends in the park. One of us holds the kite. and another one catches the line. It's exciting to see the kite flying high in the sky.

$a^2-b^2=$  ____.