It was not until Susan came back ______her close friends were waiting for him. A. which she knew B.

It was not until Susan came back ______her close friends were waiting for him. A. which she knew B. which did she know C. that she knew D. that did she know

我们先来看一下题干的结构。

原句是：
It was not until Susan came back ______ her close friends were waiting for him.
（注意最后有“for him”，可见主语 Susan 的朋友们在等的是某个男性“他”，和 Susan 自己无关，这点先不管，语法分析不受影响。）

1. 考点识别
“It was not until … that …” 是强调句结构，意思是“直到……才……”。
本句中“It was not until Susan came back”是强调句的前半部分，后面应该是“that + 主句”。
主句部分需要是陈述语序，因为 that 后面不是疑问句，也不引起倒装。

2. 选项分析
A. which she knew
B. which did she know
C. that she knew
D. that did she know

在“It was not until … that …”中，引导词必须是 that，不能用 which。所以排除 A、B。

that 后接陈述句语序：she knew，不应倒装为 did she know。排除 D。

3. 验证正确选项 C
把 C 代入原句：
It was not until Susan came back that she knew her close friends were waiting for him.
意思：“直到苏珊回来，她才知道她的密友们在等他。”
语法和语序都正确。

4. 可能的干扰
如果考生把这里当成“not until 位于句首”而倒装就错了（Not until Susan came back did she know …）。但原句开头是“It was not until …”固定句式，that 后不倒装。

所以正确答案是：