单项选择题
{{*HTML*}}
常温下将NaOH溶液滴加到己二酸(H2X)溶液中,混合溶液的pH与离子浓度变化的关系如图所示。下列叙述错误的是( )。

A.{{*HTML*}}<p>K<sub>a2</sub>(H<sub>2</sub>X)的数量级为10<sup>–6</sup></p>
B.{{*HTML*}}<p><img alt="" src="../AttachFilePick.aspx?path=\ExamPaperRes\2018\7\18\823ba3ba58e546ec827732685eb33ffd\d14cfde298d64f938e917e72b28db093.jpg" style="width: 294px; height: 43px;" /></p>
C.{{*HTML*}}<p><img alt="" src="../AttachFilePick.aspx?path=\ExamPaperRes\2018\7\18\823ba3ba58e546ec827732685eb33ffd\8844f0d7913247d7bd7df85cab6fbf83.jpg" style="width: 195px; height: 28px;" /></p>
D.{{*HTML*}}<p><img alt="" src="../AttachFilePick.aspx?path=\ExamPaperRes\2018\7\18\823ba3ba58e546ec827732685eb33ffd\50ccc90ab81a43e78e0c2f5ba14640df.jpg" style="width: 427px; height: 30px;" /></p>