Which of the following statements is correct? A: Government should tax goods with either positive or negative externalities. B: Government should tax goods with negative externalities and subsidize goods with positive externalities. C: Government should subsidize goods with either positive or negative externalities. D: Government should tax goods with positive externalities and subsidize goods with negative externalities.

Tractors and other agricultural machines greatly facilitate farming. ( ) A: communicate B: subsidize C: grade D: ease