Question

It was about 600 years ago ____ the first clock w

It was about 600 years ago ____ the first clock with a face and an hour hand was made.
A.that B.until C.before D.present

Answer 1

填that。It was ...that...构成强调句型。
整个句子翻译成：
就是大约600年前第一块拥有表面和时针的钟表问世。

Answer 2

that