Identify the phrase in bold. working crossword puzzles, the airlines passenger passed the time while waiting for his flight.

Read the following excerpt from "the city without us" by alan weisman: yet with each new acid-free rainfall, trees that still endurewill have fewer contaminants to resist as chemicals aregradually flushed from the system. over centuries, vegetation will take up decreasing levels of heavy metals, and will recycle, redeposit, and dilute them further. asplants die, decay, and lay down more soil cover, theindustrial toxins will be buried deeper, and eachsucceeding crop of native seedlings will do better. which best explains how the structure of this passage supports the author's purpose? a. the passage traces several events in the order that they will occur tohighlight how people have harmed the environment. b. the passage describes the effects of rain in the posthuman world tohighlight that nature will eventually neutralize the pollution created bypeople. c. the passage shows the effects of rain on certain plants to prove that lawsprotecting the environment are necessary for human survival. d. the passage compares the acidity of rain before and during a posthumanworld to underscore that pollution levels will remain the same.