1. Students can be categorized as "male" or "female", and "freshman", "sophomore", "junior", or "senior". We can also identify the state of residence (there are 50 states in the U.S.). How many dummy variables will be needed in a regression if you want to categorize students based on gender, class standing, and state of residence (separately, not jointly)? (4pts) A. 3 B. 4 C. 5 D. 49 E. 50 F. 51