Which of the Following Statements Is (Are) TRUE

Multiple Choice

Which of the following statements is (are) TRUE?
I. In the face of a positive externality, a perfectly competitive market produces less than the socially optimal quantity of output.
II. If vaccinations generate an external marginal benefit, their marginal social benefit will always exceed their private marginal benefit.
III. In unregulated markets, the presence of negative externalities-but not positive externalities-causes deadweight losses.

A) I and II
B) I, II, and III
C) III
D) I and III