Which situation could be considered discrimination?

Question $14$ options:

A college admissions committee accepts students solely based on their academic achievements and extracurricular activities.

An employer offers a promotion to an employee who has consistently demonstrated excellent performance, regardless of their age.

A landlord refuses to rent an apartment to someone due to their disability, despite the person having sufficient income and references.

A restaurant requires all employees to undergo a training program and some employees already have the training from previous employment.