Answer:B) He only tested one subject, so his conclusion is not valid.
Step-by-step explanation:
In a research study the sample size is most considerable element. More the sample size the reliable will be the outcome of the experiment. Thus considering only one sample for research can lead to incorrect or false results.
Here, in the given study only one sample size is taken into consideration thus the conclusion is not valid and the research study cannot be published in the journal.