A group of scientists conducted a study and used ANOVA for statistical analysis. Identify the independent variable to include the number of levels. Groups of laboratory mice from a particular ulcer-prone strain are assigned to different mazes. Maze A has no barriers and Maze B has unsynchronized stoplights and slow moving rats ahead of them. One third of the mice get beta-blockers, one third get antacids and one third get milk. After two weeks they were euthanized humanely and the size of their stomach ulcers were measured. A group of scientists conducted a study and used ANOVA for statistical analysis. Identify the independent variable to include the number of levels. Groups of laboratory mice from a particular ulcer-prone strain are assigned to different mazes. Maze A has no barriers and Maze B has unsynchronized stoplights and slow moving rats ahead of them. One third of the mice get beta-blockers, one third get antacids and one third get milk. After two weeks they were euthanized humanely and the size of their stomach ulcers were measured. A. Independent variable: treatment (6 levels) B. Independent variable: ulcer size (3 levels) C. Independent variable: mice movement speed (1 level) D. Independent variable: Maze (2