When an external cost is present in a market, the competitive market output level will be ________.

A. equal to the socially efficient level of output

B. impossible to determine

C. greater than the socially efficient level of output

D. less than the socially efficient level of output

Public goods are often supplied by a non-market institution because private firms have difficulty determining individuals' true WTP for the good due to the problem of ________.

A. non-exclusion

B. moral hazard

C. free-riding

D. adverse selection