The issue with (A) is that the stimulus provides no information about the likely location of harmful bacteria. We are told that microwaves kill the bacteria in the interior because the interior reaches high enough information, but we cannot infer that there is no bacteria on the exterior and reach any conclusion about the likely incidence of bacteria on the exterior versus the interior. It is equally likely that microwave kills both bacteria found on the exterior and interior in the absence of salt, and only the bacteria on the exterior in the presence of salt for example. For these types of question, it is important to avoid making any assumptions that are not supported by the information in the stimulus.
