—How long have you been working as an assistant here?—I finished middle school.A. Ever sin

问题补充：

—How long have you been working as an assistant here?

—I finished middle school.

A. Ever since

B. Before

C. After

D. When

答案：

(答案→)A. Ever since

B. Before

C. After

D. When

解析：词义辨析。A自从；B在…之前；C在…之后；D当…时；本题第一句的现在完成时说明所选之词必须能与现在完成时连用；只有ever since与现在完成时连用。句意：—她在这里做助手多久了？—自从我读完中学。根据句意说明A正确。