An employer who has secured compensation under the provisions of this chapter shall:

The correct choice emphasizes the requirement for an employer to keep posted in a conspicuous place printed notices stating that they have secured the payment of compensation. This is mandated to ensure that all employees are aware of their rights regarding workers' compensation and can easily access information about the employer’s coverage. By posting such notices, the employer not only complies with legal obligations but also fosters an environment of transparency. It plays a crucial role in informing employees about the existence of compensation coverage, reinforcing their rights to seek benefits in the event of an injury or work-related incident.

While the other options may involve actions that contribute to documentation or communication regarding workers' compensation, they do not specifically address the requirement for public notice. Delivering certificates to each employee or maintaining proof in a file is more about internal management rather than ensuring that the workforce is informed collectively and readily about their protections under workers' compensation laws. Therefore, maintaining a visible notice is a clear and effective way to meet these legal responsibilities.