嚴格意義上說 It was .that.才是句式 表強調.這個句式跟not until 沒有關系的
eg.:it was not until yesterday that we arrived there.（直到昨天我們才到那里）
該強調句式表達的最大特點是 將句中 it was 和 that去掉 句子仍然完整 無語病.
你后面提到的It was not until.when.也一樣 它不是某一個固定的句式.
只是比較常放在一起用 很多人便認為是一起的.
這樣句子可以造出來 但是記住它們并非是連成一體的句型
如：it was not until late at night when you had already fell asleep that we arrived there.
直到夜深了,你早已入睡,我們才到那里.
不知道我表達的夠不夠清楚 歡迎追問It was not until last year _______ their plan was approved. A.whenB.that此題的答案給的是：A不知怎么解釋？謝謝你確定是A么個人覺得是that It was not until last year thattheir plan was approved.表示強調。去掉it was和 that ：Notuntil last year ， their plan was approved.