(a) HOOC-[CH2]4-COO-C2H5 + 2NaOH → NaOOC-[CH2]4-COONa (X1) + C2H5OH (X2) + H2O
(b) NaOOC-[CH2]4-COONa + H2SO4 → HOOC-[CH2]4-COOH + Na2SO4
(c) nHOOC-[CH2]4-COOH + nH2N-[CH2]4-NH2 → nilon-6,6 + 2nH2O
(d) HOOC-[CH2]4-COOH + 2C2H5OH → H5C2OOC-[CH2]4-COOC2H5 → Đáp án B