Task: Question Answering
Input (English): A scientist plans to investigate the nervous system of sea slugs. What should the scientist do first?  
 (A) Develop a theory about sea slugs that can be tested. (B) Go to the ocean to observe the behavior of sea slugs. (C) Obtain several sea slugs and conduct experiments with them. (D) Review the research other scientists have done on sea slugs.
Output (English): D