Question ID:PT90 S2 Q21 Passage:A geologist recently claimed to have discovered in clay a previously unknown form of life:   "nanobes," one-tenth the size of the smallest known bacteria. However, it is unlikely that nanobes truly are living things. They are probably inanimate artifacts of the clay's microscopic structure, because a nanobe is too small to contain a reproductive mechanism, a prerequisite for life. Stem:Which one of the following, if true, most seriously weakens the argument? Correct Answer Choice:BChoice A:No known form of bacteria is complicated enough in structure to engage in a sexual type of reproduction. Choice B:Single-celled creatures can combine to form a multicelled structure and then reproduce before they disband into separate single cells again. Choice C:The material phenomena that some scientists claim are the fossilized remains of bacteria in meteorites from Mars are approximately the same size as nanobes. Choice D:Previous definitions of life were based on research done with inferior microscopes no longer in use. Choice E:Animals such as cold-blooded lizards can be physiologically simpler, though still larger, than other animals.