Which paragraph best helps the reader understand the range of kettering inventions

Which line in this excerpt from the great gatsby by f. scott fitzgerald contains a simile? about half way between west egg and new york the motor-road hastily joins the railroad and runs beside it for a quarter of a mile, so as to shrink away from a certain desolate area of land. this is a valley of ashes—a fantastic farm where ashes grow like wheat into ridges and hills and grotesque gardens where ashes take the forms of houses and chimneys and rising smoke and finally, with a transcendent effort, of men who move dimly and already crumbling through the powdery air. occasionally a line of grey cars crawls along an invisible track, gives out a ghastly creak and comes to rest, and immediately the ash-grey men swarm up with leaden spades and stir up an impenetrable cloud which screens their obscure operations from your sight.

Which lines from the speech best supports this topic sentence? and as we walk, we must make the pledge that we shall always march ahead. we cannot turn back. there are those who are asking the devotees of civil rights, "when will you be satisfied? " and they have come to realize that their freedom is inextricably bound to our freedom. we cannot walk alone. we refuse to believe that there are insufficient funds in the great vaults of opportunity of this nation. and so we've come to cash this check, a check that will give us upon demand the riches of freedom and the security of justice. and so let freedom ring from the prodigious hilltops of new hampshire. let freedom ring from the mighty mountains of new york. let freedom ring from the heightening alleghenies of pennsylvania.

What is the independent cause in this sentence? "if the poem is about going mad when love is lost, what would happen if love didn't die? "