Which of the following is NOT a common-law duty of an employer?

The assertion that assumption of risk is NOT a common-law duty of an employer is accurate. Common-law duties are obligations that arise from judicial decisions rather than statutes. Employers have specific responsibilities towards their employees to ensure their safety and well-being while at work.

The duties to warn workers of inherent dangers, provide a safe working environment, and ensure an adequate number of competent fellow workers are all established responsibilities that employers must uphold to protect their employees. These duties are integral to maintaining a safe workplace and preventing injuries.

On the other hand, assumption of risk pertains to the legal doctrine where employees may accept the inherent risks associated with their job and can sometimes limit an employer's liability. This concept does not impose a duty on the employer; instead, it reflects a scenario where the employee acknowledges certain risks associated with their employment. Thus, assumption of risk is not a duty that employers are required to fulfill, distinguishing it from the other responsibilities listed.