Final answer:
According to the provisions of the WARN Act, a healthcare consulting company with more than 100 employees must notify the employees 60 days prior to a layoff.
Step-by-step explanation:
According to the provisions of the WARN Act, when a healthcare consulting company with more than 100 employees is laying off 60 employees, they must notify the employees 60 days prior to the layoff. The WARN Act requires employers with more than 100 employees to provide written notice 60 days before plant closings or large layoffs. Therefore, option D is correct - the healthcare consulting company must notify the employees 60 days prior to the layoff.