Something there is that doesn't love a wall, that sends the frozen-ground-swell under it, and spills the upper boulders in the sun; and makes gaps even two can pass abreast. the work of hunters is another thing: i have come after them and made repair where they have left not one stone on a stone, but they would have the rabbit out of hiding, to the yelping dogs. the gaps i mean, no one has seen them made or heard them made, but at spring mending-time we find them there. whom does the speaker blame for the gaps in the wall?

the reason some people sacrifice their own life for another person's life could be that they are in love with them and would do anything to keep them safe a protected even if that means risking their life in the process

the sentence that avoid faulty coordination is:

culture, which is well represented in philadelphia, plays a major role including theatre, music, and the visual arts.  

faulty coordination occurs when the writer gives equal importance two different ideas (clauses) which in fact are not equivalent. in order to correct a misplaced clause or idea, the writer can place less important or emphatic ideas in a relative clause as in the previous sentence.