Final answer:
An example of compare-and-contrast structure in paragraph 4 is when Johnson acknowledges the argument against the Highway Beautification Act and provides a rebuttal.
Step-by-step explanation:
The example of compare-and-contrast structure in paragraph 4 of the text is when Johnson acknowledges that some people may argue against the Highway Beautification Act because they believe it gives the government too much power over individual states. Johnson states, "Of course, we recognize that some people will criticize these proposals -- some people will say that they grant the Federal Government too much power to restrict the prerogatives of the States and the people." This is a compare-and-contrast structure because Johnson acknowledges the opposing argument (that the Act grants the government too much power) and then provides a rebuttal to it by stating that the Act is necessary to preserve the beauty of the nation's highways.