区分有效群团和无效群团的标准是( )A．权力大小 B．产生原因 C．规模大小 D．

A: Can you tell me something about the southern Chinese tigers?
B: Sure, (1)__________
A: Why? Are they endangered?
B: Yes. There used to be a lot of southern Chinese tigers, but now (2)__________
    Since then the government has done something to protect them.
A: (3)__________
B: Their favorite habitat is the mountains full of trees.
A: And (4)__________
B: Many of the trees have been cut down, so (5)__________
A: I see, thank you.