问题
选择题
The book was written in 1946, ____ the education system has witnessed great changes.
A．when
B．during which
C．since then
D．since when
答案
答案：D
考查定语从句。since when以为“从那时起”，when时间副词，这里指代时间 1946，相当于since when的意思就是since the year 1946。句意：自从1946年起，教育体系经历了巨大变革。