For many thousands of years, because humans did not understand fire or how to harness it for cooking, how did they eat their food?

Thousands of years back people were mostly hunters and gatherers. Thus,  they used to eat raw meat and vegetable since they didn't know anything about cooking raw food in fire. After discovering about cooking raw meat and vegetables in fire is when new dishes and inventions came about.

answer; (c); to assure that workers have the right to a safe workplace and that it is the employer's responsibility to provide safe and healthy workplace;