If an Employer Is Sued for Age Discrimination, Which of the Following

If an employer is sued for age discrimination, which of the following defenses are not open to that employer?

A) the employee was dismissed for good cause
B) the employee did not do her work properly
C) sex is a bona fide occupational qualification
D) younger workers are cheaper to employ than older workers
E) the employer was observing a bona fide seniority system