Riddle # 3. Murder at school
On the first day of the new school year, during the last break, the body of the geography teacher is found in one of the classrooms. The police have four suspects: the gardener, the math teacher, the sports teacher and the school principal. Here is their respective alibi at the time of the murder:
- The gardener was planting shrubs in the backyard.
- The math teacher was watching the mid-year exam.
- The sports teacher played basketball with his students.
- The director was in his office.
Following these statements, the police arrest the culprit. Who killed the geography teacher and how did the police identify the murderer?