Which are valid?

A: All teachers grade papers. Cindy is grading papers, so she is a teacher.
B: Everyone who is on the team was at practice. Donna was at practice, so she is on the team.
C: All state employees were off on Labor Day. Debra is a state employee, so she was off on Labor Day.
D: Everyone in Miss Easy's class was exempt from the exam. Kathy is in Miss Easy's class, so she was exempt from the exam.