Answer - D. Mitosis (Confidently Correct)
Reasoning - Its basically the process when the chromosomes move during the ends of each section. Until then it becomes closed into a new cell.
The answers are stress accumulations and reoccurrence! I hope this helped you and I hope you have a great day! :)
First, he should measure how long it takes for the liquid to become clear if X and Y are mixed together. Then, he should measure how long it takes if he also adds substance A to X and Y. He will find out if substance A is a catalyst.