某无色溶液中加入过量盐酸有沉淀产生，过滤后向滤液中加入过量氨水又有沉淀产生，下列溶液中符合此条件的是（　　）

A．Ag⁺、Al³⁺、K⁺、Cl^-

B．SiO₃^2-、AlO₂^-、K⁺、Na⁺

C．Ag⁺、Cu²⁺、Na⁺、NO₃^-

D．Ag⁺、Ba²⁺、Na⁺、Br^-

In my opinion, everyone has periods in their lives _______ everything seems very hard.

A．when

B．where

C．which

D．that