The spotted hawk swoops by and accuses me, he complains of my gab and my loitering. i too am not a bit tamed, i too am untranslatable, i sound my barbaric yawp over the roofs of the world. the last scud of day holds back for me, it flings my likeness after the rest and true as any on the shadow'd wilds, it coaxes me to the vapor and the dusk. i depart as air, i shake my white locks at the runaway sun, i effuse my flesh in eddies, and drift it in lacy jags. i bequeath myself to the dirt to grow from the grass i love, if you want me again look for me under your boot-soles. you will hardly know who i am or what i mean, but i shall be good health to you nevertheless, and filter and fibre your blood. failing to fetch me at first keep encouraged, missing me one place search another, i stop somewhere waiting for you. what is one purpose of the imagery in this poem? 

a. to compare the speaker to a silent mountain at dawn
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b. to put emphasis on the phrase, "i too am untranslatable"
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c. to make the sound of the speaker's voice seem vivid
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d. to paint a picture in the reader's mind of sand dunes