Which of the following should employers do to actively prevent workplace hazards?

It is not possible to eliminate all hazards. Some occupations have inherent hazards that employees are aware of. Emergency drills should be conducted on a regular basis to insure that they are still adequate. On-site first aid is not a requirement. OSHA regs state that "in absence of an on site infirmary" an employer must have people with first aid training and supplies available.