The principal-agent problem could be defined by saying that it is an agent who benefits from the effort of others without having even participated in the joint effort. It is a concept that is to be linked more broadly to the problems of information asymmetry.
The term moral hazard refers to a type of market failure where the existence of insurance against a certain risk increases the likelihood of the occurrence of the event causing the risk.
The right answer is:
Principal-agent problem matches with 2
Asymmetric information matches with 3
Adverse selection matches with 4
Moral hazard matches with 1