In fahrenheit 451 what are the symbols sieve and the sand for?

What is the meaning of the word checking as it is used in this sentence from the second paragraph of the passage?

What is the theme of the poem, my tongue is divided into two by quique aviles? my tongue is divided into twoby virtue, coincidence or heavenwords jumping out of my mouthstepping on each otherenjoying being a voice for the messageexpecting conclusionsmy tongue is divided into twointo heavy accent bits of confusioninto miracles and accidentssaying things that hurt the heartdrowning in a language that lives, jumps, translatesmy tongue is divided by natureby our crazy desire to triumph and conquerthis tongue is cut up into equal piecesone wants to curse and sing out loudthe other one simply wants to ask for watermy tongue is divided into twoone side likes to partythe other one takes refuge in prayingtongueenglish of the funny soundstonguefunny sounds in englishtonguesounds funny in englishtonguein funny english soundsmy tongue sometimes acts like twoand it goes crazynot knowing which side should be speakingwhich side translatingmy tongue is divided into twoa border patrol runs through the middlefrisking wordsasking for proper identificationchecking for pronunciationmy tongue is divided into twomy tongue is divided into twoi like my tongueit says what feels righti like my tongueit says what feels rightby quique aviles

Me ! select the correct answer. which sentence is an oxymoron? a. to have peace, we must go to war. b. a glass can be viewed as either half full or half empty. c. the lawyer was deceptively honest with his clients. d. spies do not dress like spies. e. though the lab was messy, there was a method to his madness.