Answer:
The option that weakens the argument is that "Professor Hathaway’s research can be used by other scientists to create useful applications". Therefore option C is the most correct option.
Explanation: Every since research has a method and every method has a step of application. Because Professor Hathaway research is a scientific research, Hathaway should be using a Scientific method in the research work, which can be traceable by other scientist to continue the research work.
Professor Hathaway's research work may not be easy for a scientist, that has not been working together with him in the research work. But it doesn't mean that the research has ended due to his untimely death. If a proper study is given to the research previously made by the professor, the results of the previous work would tell the next step of his work, which can be continued by any scientist that is disciplined in the area of his research.
The argument will not stand because, they exist many other professors in his area of discipline that can continue the research from where he stopped, and give the work a practical approach.