Which economic concept is the closest to the saying, "There's no such thing as a free lunch"?

Fill in the blank: The Players Union went on strike against the NBA during the 1998-1999 season, canceling games for weeks

Other things constant, the strike and subsequent cancellation of games would tend to ________ the price elasticity of demand for hockey tickets during the same period the NBA games were canceled. A) worsen B) preserve C) increase D) decrease

There are four lighthouses on the island of Sand. If this is the efficient quantity of lighthouses, ________

A) the marginal social benefit of the fourth lighthouse equals its marginal social cost B) total social benefit is zero C) marginal social benefit minus marginal social cost is a maximum D) Both answers A and C are correct.