It was not until ... that ..., sau "that" nhớ bỏ (didn't) nhưng các trường hợp (couldn't/ weren't/ wasn't/ hadn't) sau that chỉ bỏ "not" mà thôi.
47. We didn't study English until we began primary school.
-> It ..................................................................................................
48. I didn't learn English until 2002.
-> It ...................................................................................................
49. He didn't know how to swim until he was 30.
-> It ....................................................................................................
50. They didn't begin to learn English until 1980.
-> It .....................................................................................................
47. We didn't study English until we began primary school.
\(\Rightarrow\) It was not until we began primary school that we studied English.
48. I didn't learn English until 2002.
\(\Rightarrow\) It wasn't until 2002 that I learned English.
49. He didn't know how to swim until he was 30.
\(\Rightarrow\) It It was not until he was 30 that he knew how to swim.
50. They didn't begin to learn English until 1980.
\(\Rightarrow\) It It was not until 1980 that they began to learn English.