— They speak perfect English. How long have they learnt it?
— they were seven years old.
A. Since
B. When
C. After
D. Until
网友回答
(答案→)A. Since
B. When
C. After
D. Until
解析：A. Since自从，后接一般过去时，主句用现在完成时 B. When当…时候C. After 当…之后 D. Until直到…;句意：他们说英语说得非常的好。他们学习它多长时间了？自从他们7岁的时候。故选A