这道题的答案是什么？---**Question Stem:** 4. 某研究小组设计如下图电解池，既可将中性废水中的硝酸盐转化为氨，又可将废塑料(PET)碱性水解液中的乙二醇转化为羟基乙酸盐，实现变废为宝。 **Diagram Description:** * **Type:** Electrolytic cell diagram. * **Main Elements:** * Two cylindrical electrolytic cell compartments are shown, separated by an "阴离子交换膜" (anion exchange membrane) in the middle. * Each compartment contains a vertical rectangular electrode. * An external DC power source is connected to the electrodes: the left electrode is connected to the negative terminal (cathode), and the right electrode is connected to the positive terminal (anode). * **Left Compartment (Cathode):** * An arrow indicates NO₃⁻ (nitrate ion) entering. * An arrow indicates NH₃ (ammonia) exiting. * **Right Compartment (Anode):** * An arrow indicates CH₂OH-CH₂OH (ethylene glycol) entering. * An arrow indicates CH₂OH-COO⁻ (hydroxyacetate ion) exiting. * **Relative Position:** The anion exchange membrane is positioned between the two electrodes, allowing anions to pass. * **Implicit Processes:** * In the left compartment (cathode), NO₃⁻ is reduced to NH₃. * In the right compartment (anode), CH₂OH-CH₂OH is oxidized to CH₂OH-COO⁻. **Question Prompt:** 电解时，下列说法错误的是 **Options:** A. 阳极区pH下降 B. OH⁻从阴极区向阳极区迁移 C. 阴极发生反应 NO₃⁻ + 7H₂O + 8e⁻ = NH₃·H₂O + 9OH⁻ D. 阴极转化1mol NO₃⁻，阳极将生成4mol HOCH₂COO⁻