“逆水行舟，一篱不可放缓；滴水穿石，一滴不可弃滞。”这句话蕴含的哲理是（  ）

苔藓植物有根、茎、叶分化，所以能在多种环境中生活．

函数y= $\frac{\sqrt{4-x^2}}{x^2-\left|x\right|}$ 的定义域为____．

种群内个体的空间分布以随机分布最为常见．（    ）

Lucy： Hello, Mary, you look really tired. What's the matter?

Mary： I didn't go to sleep ____ midnight last night so I didn't get enough sleep.

Lucy： Sorry to hear that. Why don't you go to sleep ____ (early) tonight?

Mary： I hope so, ____ I have two after—school classes today. So I can only start ____ (study) after dinner.

Lucy： Maybe you should tell your parents ____ you can't do so many things.

Mary： I did, but they think it's important that I take more after—school ____ (class).

Lucy： Well, they ____ (possible) want you to get into a good senior high school.

Mary： Yes, I guess that's ____ reason.

Lucy： You should talk to your parents again. Explain that you need to get enough sleep to stay ____ (health).

Mary： That's a good idea. OK, I'll try to talk to ____ (they) again.