PT 28 Sec 3 Q 12

[bk1]

I interpreted this as "if the above is true, which of the following could be true." To me this leads to C and E. C must be true and E could be true, but C is right. So either I don't see why E can't be true or I didn't see why the question is asking "must be true" rather than "could be true."

[Cambridge LSAT]

The letter writer claims that the studies prove that vexone has been utilized effectively against all (more than 4,000) of the species in North America. However, if it was tested against exactly 4,000 species, the possibility remains that it is ineffective against some of the untested species.