Final answer:
Compulsory insurance prevents adverse selection by requiring everyone to have coverage, which spreads the risk across a larger pool of individuals.
Step-by-step explanation:
Compulsory insurance helps prevent adverse selection, which is the tendency for high-risk individuals to seek insurance coverage more than low-risk individuals. This is achieved through option b) by requiring everyone to have coverage, spreading the risk. When everyone is required to have insurance, the risk is spread across a larger pool of individuals, which helps to balance out the costs and prevent insurance companies from only attracting high-risk individuals.