Mr. Smith graduated from college at the age of 23 and he has been working as a teacher i

问题补充：

Mr. Smith graduated from college at the age of 23, and he has been working as a teacher in a middle school.

A. after that

B. from then on

C. from then

D. since then

答案：

A. after that

B. from then on

(答案→)C. from then

D. since then

解析：可联系答.案.网客服索取。