In Which of the Following Cases Will an Employer Be

In which of the following cases will an employer be justified in upholding random testing for drug use by an employee?

A) The employee poses a safety risk to others by doing a job while under the influence of drugs.
B) The employee has been informed orally about the company's random drug-testing policy.
C) The employee does not undertake a periodic physical examination.
D) The employee had failed his pre-employment drug test.