1、单选题：
For fish growth in the aquatic ecosystem, dissolved oxygen is a（ ）。
选项：
A:general ecological factor
B:limiting factor
C:abiotic factor
D:biotic factor
答案: 【limiting factor】

2、单选题：
Which of the following factors is not the limiting factor for fish growth in the aquatic ecosystem?（ ）
选项：
A:DO
B:Silt
C:Temperature
D:Soil nutrients
答案: 【Soil nutrients】

3、单选题：
Humans raising cattle for food is what kind of relationship?（ ）
选项：
A:parasitism
B:predation
C:intraspecific competition
D:mutualism
答案: 【predation】

4、单选题：
Which is the abiotic factor of an organism’s environment?（ ）
选项：
A:plants
B:weather
C:fungi
D:bacteria
答案: 【weather】

5、单选题：
Which is not the typical habitat of mosses?（ ）
选项：
A:shady
B:drought
C:cool
D:moist
答案: 【drought】