下列关于生态系统物质循环和能量流动的叙述中,正确的是( )
A:在生态系统中二者同时进行,周而复始
B:如果把作物秸秆当燃料烧掉,生态系统中的碳就不能有效地进行循环
C:二者是生态系统的主要的功能,可以通过食物链来实现
D:物质在沿着食物链流动的过程中是逐级递减且单向流动的,而能量是可循环的
One day Skygirl went to our classroom with Skyboy. She was very h____. She took a hamburger and a cola w____ her. She wanted to r____, to have some food and drink and t____ to boys and girls in the classroom. She was not happy when she saw the s____ in the classroom. What does the sign mean? It says: "Don't run in the classroom. Don't talk to each other in class. Don't ear or d____ in class. ""I don't want to be in the classroom. Let's f____ away. "The Supergirl said to the Superboy. They came to the Garden City. Garden City is an i____ place for the Superchildren to play.
Do you want to helped them?
____改为____