Trainer gets the questions well in advance.
Trainer can get the key and solutions too well in advance.
Trainer can refer study notes/materials.
Trainer can take his time to solve the questions
Trainer can afford to make mistakes and correct it.
Trainer can skip the questions.[ and still got nothing to lose!]
Trainer can't afford to come late to class.
Trainer can't afford to sleep/message in class.
Trainer can't afford to guess the answers.
Trainer can't afford to know only one way to solve the questions.
Trainer can't afford to appear dumb or stupid.
Trainer can't afford to look younger than the trainees of the class :):)
1)Good coaches need not be good players. Good players need not be good coaches.
2)After being on both the ends of the spectrum, Trainee and trainer of competitive exams.