Questions 22 to 25 are based on the conversation you have just heard.

A．Some friends and relatives that she had no time to visit before.

B．The closest friends and relatives.

C．The friends and relatives that helped her a lot.

D．Some friends and relatives that would get upset if she doesn’t visit.

在一定地域内生物与环境所形成的统一整体叫做生态系统．下列不属于生态系统的一是（　　）

A．一只空鱼缸

B．一个养鱼池

C．一个小湖泊

D．一条小河