Choice A is the best answer. While the author predominantly supports the use of public transportation, in the third paragraph he recognizes some limitations to the public transportation system: it is a "depressing experience" (lines 25-26"America...on") and "underfunded, ill-maintained, and ill-planned" (line 31"underfunded...Given").
Choices B, C, and D are incorrect because the third paragraph does not expand upon an argument made in the first two paragraphs, provide an overview of a problem, or advocate ending the use of public transportation.