Answer: B (\(\text{C}_{12}\text{H}_{22}\text{N}_2\text{O}_2\)). Nylon is a polyamide made by condensation polymerisation between the diamine X, H₂N–(CH₂)₆–NH₂, and the dicarboxylic acid Y, HOOC–(CH₂)₄–COOH. Each time an amide link –CO–NH– forms, one molecule of water is eliminated. Joining one X to one Y forms two amide links, so two water molecules are lost per repeat unit.
Counting atoms, X is C₆H₁₆N₂ and Y is C₆H₁₀O₄, so together they give C₁₂H₂₆N₂O₄. Removing 2H₂O subtracts 4 H and 2 O, leaving \(\text{C}_{12}\text{H}_{22}\text{N}_2\text{O}_2\).
This matches option B. Common error: forgetting to remove two water molecules, or removing only one, which would leave too many H and O atoms. The answer is B.
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