Which defense(s) would you advise an employer to rely on in the following cases of prima facie discrimination?

Which defense(s) would you advise an employer to rely on in the following cases of prima facie discrimination? Assume that all the defenses are available in Alberta Human Rights.

The employer refuses employment to a person in a wheelchair because the job requires employees to be able to stand for long periods of time.

A Christian high school gives hiring preference to Christian teachers.

A department store employer fires an employee who, for religious reasons, cannot work on Saturdays, the busiest day of the week.

A university refuses employment to a professor who has a vocal disability that prevents her from lecturing in large lecture halls.

An employee is fired when he reaches age 65 because the employer’s pension plan includes a mandatory retirement clause.

An organization that provides services and counselling to abused women has a policy of hiring only women.