My grandfather suffered a lot during World War Two___ broke out in the 1939.
问题描述：
My grandfather suffered a lot during World War Two___ broke out in the 1939.
y grandfather suffered a lot during World War Two___ broke out in the 1939.
这里为什么填which,而不填 when ?
答
用when后面得改成when it broke out in the 1939.
否则后句没主语了