In a learning experiment a researcher ran rats through a maze. Some of the rats were blind, others deaf, others lacked a sense of smell, and others had no sensory deficiencies; yet all the rats learned the task in much the same amount of time. Of the senses other than sight, hearing, and smell, only kinesthesia had not previously been shown to be irrelevant to maze-learning. The researcher concluded on the basis of these facts that kinesthesia, the sensation of bodily movement, is sufficient for maze-learning. The researcher's reasoning is most vulnerable to which one of the following criticisms? ['The possibility that the interaction of kinesthesia with at least one other sense is required for maze-learning cannot be ruled out on the basis of the data above.', 'It can be determined from the data that maze-learning in rats depends on at least two sources of sensory stimulation, one of which is kinesthesia, but which of the remaining sources must also be employed is not determinable.', 'The small differences in proficiency found by the researcher did not appear to fall into a systematic pattern by group.', 'It can be determined from the data that rats can learn to run mazes by depending on kinesthesia alone, but the possibility that rats respond to nonkinesthetic stimulation is not ruled out.']