Answer:
effectiveness/quality.
Step-by-step explanation:
When choosing a health product or service the most important characteristic is its effectiveness/quality. Unlike other types of products, the entire reason an individual would purchase a health product or service is that they absolutely need it to improve their quality of life or in some cases continues living. Therefore, you want the product/service that you purchase to be as effective as possible so that it provides the benefits that you are in dire need of. This is why, unlike products such as those for entertainment purposes, the main characteristic should be the product's effectiveness/quality.