My parents ____ (marry) for 25 years.

“○”和“●”表示不同元素的原子，下图表示单质的是（   ）

一般来说．生态系统中生物的____ 越多，____ 和____ 越复杂，生态系统的自我调节能力就越强．

阅读短文，选择正确的答案。

    Chen Jie and Chen Lin are sisters. Chen Jie is 14. She's 2 years younger than Chen Lin. But she's taller than Chen Lin. Chen Jie is 46 kilograms. She's l kilogram heavier than Chen Lin. Chen Jie likes sports. She plays sports every day. So she's stronger than Chen Lin. Chen Jie has short hair, but Chen Lin has long hair. They often wear the same size shoes. They wear size 36. They love each other.

加上不同偏旁，变新字，再组词。

土____  ____    

   ____  ____

   ____  ____