请教一道LR

Publicity campaigns for endangered species are unlikely to have much impact on the most important environmental problems, for while the ease of attributing feelings to large mammales facilitates evoking sympathy for them, it is more difficult to elicit sympathy for other kinds of organisms, such as the soil microorganisms on which large ecosystems and agriculture depend.

Which one of the following is an assumption on which the argument depends?

A The most imprtant environmental problems involve endangered species other than large mammals.

不明白为什么the problem 必须要involve endangered species

既然问了为什么，那么你就问问自己，如果没有involve endangered species会产生怎样的后果呢？结果必然是原文的结论得不到