It was about 600 years ago the first clock with a face and an hour hand was made .Athat

问题补充：

It was about 600 years ago the first clock with a face and an hour hand was made .

Athat

B. until

C. before

D. when

答案：

(答案→)A. that

B. until

C. before

D. when

解析：这是一个强调句，强调时间状语about 600 years ago。