The Great wall is the only one of the buildings on the earth_____ seen from the moon.

A．which is

B．which are

C．that are

D．that is

a、b、c、d、e分别为MgC1₂、KHSO₄、KOH、NaHCO₃、A1C1₃溶液中的一种，已知：①a能与其他4种溶液反应，且a与c、e反应时有明显现象；②b与d反应只产生气泡；③e只能与a反应。下列推理不正确的是(   )

A．a一定是KOH

B．c一定是A1C1₃

C．e一定是MgC1₂

D．b一定是KHSO₄