Would you like noodles           vegetables?

生态平衡是一种（  ）

阅读理解。根据短文内容，选择正确答案。

    A lot of boys and girls in west countries are wearing the same kinds of clothes: Many of them have long hair, so it is often difficult to tell whether they ate boys or girls.

    One day, an old man went for a walk in Washington. When he was tired he sat down on a long chair. A young person was standing onthe other side of the pool.

  “Good Heavens!” the old man said to the person who was sitting next to him on the chair. “Do you see that person with long hair? Is ita boy or a girl?”

  “A girl.” said his neighbor, “She's my daughter.”

  “Oh!” the old man said quickly, “I'm sorry. I didn’tknow that you were her mother.”

  “I'm not,” said his neighbor, “I'm her father.”

由于不知道表中各种液体之间比热容的大小关系，还需要用实验方法得到实验器材：铁架台（带铁圈）、石棉网、温度计、细线、火柴、烧杯、秒表、天平和砝码（以上每一种器材数量足够、规格相同）；火焰相同的酒精灯若干；密度表中所给出的各种液体足量，实验中，小明选取的三种液体分别是煤油、植物油和水．

一质量为m的球放在倾角为30°的光滑斜面上，某人用水平力推球使球处于静止状态，则人对球的推力与斜面对球的支持力分别为多大？