The correct answer is: "they generate positive externalities and ensure sustainability".
A positive externality is a benefitial effect for a third party which arises from an economic transactions. For example, if environmental protection laws are enacted and business are binded by them, their economic activity with be respectful with other members of the society and provide social welfare.
Moreover, such regulations permit the development of a sustainable economic model, which worries for keeping the environment in a healthy balance.