Geometry

Question Analysis  
This question applies mutual exclusivity to a real-world scenario.  

Key Concept Explanation  
Mutually Exclusive: Only one light color can be active at a time.  P(A or B) = P(A) + P(B)
Exhaustive Outcomes: Red, yellow, green cover all possibilities.  

Step-by-Step Solution  
1. Total possible colors: 3 (red, yellow, green).  
2. P(Red) = 1/3.  
3. P(Green) = 1/3.