Answer:
a. the injured demanding compensation through a class-action law suit
Step-by-step explanation:
A Coase theorem, developed by Ronald Coase, states that when the transaction costs is very low, the two parties will have the benefit to bargain and arrived at an efficient outcome or conclusion in the presence of an externality.
Accordingly, when the leakage of dangerous radiations which was leaked during the Tsunami hitting the nuclear power plant could have been prevented, then as the Coasian solution to externality would be filing a class action law suit by the injured people demanding compensation for the damage.
Hence the correct option is -- (a)