Answer:
B. adverse selection.
Explanation:
Because, the restaurant price is a flat fee the person which find this attractive are those who eat above average.
Liek a life insurance per life will be taken with people who's life expectancy is above average, the same occrus here.
People who eat less than average will have less incentive to go
while above average move incentive thus, the "real" average including the adverse selection qualms should be more higher than the average across all consumers.