Final answer:
The distinct WHMIS border is a requirement on the supplier label, which is one of the key components in the labeling of hazardous products in the Workplace Hazardous Materials Information System.
Step-by-step explanation:
The question refers to the Workplace Hazardous Materials Information System (WHMIS), a comprehensive system for providing health and safety information on hazardous products intended for use, handling, or storage in Canadian workplaces. Specifically, the question asks about the necessity of the distinct WHMIS border, which is an element of the communication standard used for labeling hazardous products. The distinct WHMIS border is a requirement on c) the supplier label. Supplier labels are an essential part of this hazard communication system and they must have a distinctive hatched border to be easily recognizable. These labels must also contain other critical information such as the product name, hazard symbols, risk phrases, precautionary measures, and the supplier's name and address.