The Hazard Communication Standard (HCS) indeed requires employers to perform several key actions to ensure the safe handling of hazardous chemicals. However, among the options you've provided, the statement that is NOT a requirement of the HCS is:
Prepare and post a list of all employees who handle hazardous and toxic substances in the workplace.
While employers must ensure that employees are aware of the hazards of the chemicals they work with, there isn't a requirement specifically to prepare and post a list of employees who handle those substances. The other three actions—obtaining Safety Data Sheets (SDS), labeling containers, and training employees—are clearly outlined requirements of the HCS.