It was probably in that moment ____ I understood what kindness

It was probably in that moment ____ I understood what kindness really was.
A、which
B、when
C、that
D、what
【正确答案】：C
【题目解析】：【考点点击】本题考查强调句型。【要点透析】其句型为“It+be+被强调部分+that+分句”,本句的强调部分为时间状语,故空处应填 that