Đáp án A
H2N-CH2-COOC2H5 (X) + NaOH → t ° H2N-CH2-COONa (X1) + C2H5OH
H2N-CH2-COONa (X1) + 2HCl (dư) ClH3N-CH2-COOH (X2) + NaCl
ClH3N-CH2-COOH (X2) + CH3OH (khan) → t ° . HCl ClH3N-CH2-COOCH3 (X3) + H2O
ClH3N-CH2-COOCH3 (X3) + 2KOH → H2N-CH2-COOK + KCl + CH3OH
Vậy X2 là ClH3N-CH2-COOH.