Final answer:
The answer to the student's question is 'guidelines', which are used in health care systems to select providers and assure quality care, ensuring the integrity of health services and providing protection against adverse selection in insurance markets.
Step-by-step explanation:
There are usually explicit guidelines for selecting providers and a formal procedure to assure quality care. The correct answer is a) Guidelines. In health care systems, whether it's a fee-for-service or through health maintenance organizations (HMOs), there are typically established guidelines to ensure that medical care providers are chosen based on specific standards and that the care provided meets quality requirements. These guidelines are essential for maintaining the integrity of the health care system and for protecting patients against adverse selection, where individuals with more knowledge about their health risks may affect the balance of insurance markets.