It was not until he had lost his health （ ） he got to know its value.
A、
that
B、
until
C、
what
D、
when
【正确答案】：A
【题目解析】：
本题考查强调句的判断与使用。
去掉it was以及空缺处连词后，句意依然完整，故本句符合强调句结构：It is/was+(被强调部分)+that+句子剩余部分，被强调部分为时间状语“not until he had lost his health”，A选项符合题意。
句意：直到他失去了健康，他才开始明白它的价值。