It was not until I had read your letter that I understood the true state of affairs.
直到我读了你的信，我才明白了事情的真相。
我明白这个句子的意思,但是我不能分析这个句子的结构。请分析。
这是个标准的强调句型: It is (was) A that。这个句型中的 A 是被强调的成分, 它可以是个单词或短语, 也可以是个分句, 例如, not until I had read your letter (它是全句的信息焦点)。上面的句子的非强调句型是: I didn't understand the true state of affairs until I had read your letter.
类例：
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It was not until I saw Margaret next morning, however, that I felt happy. (Snow) 直到我第二天早晨见到玛格丽特，才感到高兴。
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It was not until a Saturday afternoon in May that Margaret could arrange for me to meet her elder sister. (Snow) 直到五月的一个星期六的下午,玛格丽特才为我安排好去见她的姐姐。
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It was not until his third match in 1790 that he finally beat Humphries and became Champion of England. (New Concept English, Book 3, L.21) 直到 1790 年，在第三次比赛中，他终于击败了 Hamphries，而成为英国的冠军。
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It was not until this instant that he truly realized what he was about to do, and what awaited him inside. (Dan Brown, The Da Vinci Code) 直到此时此刻他才真正意识到自己要做 什么,里面有什么在等着他。(《达·芬奇密码》)
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It wasn't until I became President that he took me off the tricycle and put me in a pickup truck. (B. Clinton, My Life) 直到我当上总统，他才让我走下三轮自行车，把我放到了一个轻型货车里面。（《我的生活》）
请做下面的英语试题：
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It was ____ late in the evening that the explorers pitched camp. A. before B. when C. till D. not until(全国研考)
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It was not ____ she took off her dark glasses ____ I realized she was a famous film star. A. when; that B. until; that C. until; when D. when; then(全国高考,92-30)
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____ she realized it was too late to go home. A. No sooner it grew dark than B. Hardly did it grow dark that C. Scarcely had it grown dark than D. It was not until dark that(全国四级,00.1-61)