20. HCequiv CHxrightarrow [Delta ](NaH)arrow A(CH_(3)I)/(-272)arrow B(NaNH_(3))/(-272)arrow Cxrightarrow [CH_(3)I](H_(2)S)Dxrightarrow [H_(2)SO_(4)H_(12)O]

The correct answer is D.<br /><br />In this reaction sequence, the compound HC≡CH (acetylene) undergoes a series of transformations to ultimately produce compound D.<br /><br />1. The first step involves the reaction of acetylene with sodium hydride (NaH) to form compound A, which is an acetylide ion.<br /><br />2. The second step involves the reaction of compound A with methyl iodide (CH3I) at a low temperature (-272°C) to form compound B, which is an alkane.<br /><br />3. The third step involves the reaction of compound B with sodium amide (NaNH3) at a low temperature (-272°C) to form compound C, which is an alkyne.<br /><br />4. The fourth step involves the reaction of compound C with hydrogen sulfide (H2S) to form compound D, which is an alkane.<br /><br />5. The final step involves the reaction of compound D with sulfuric acid (H2SO4) and water (H2O) to form the final product.<br /><br />Therefore, the correct answer is D.