Open Day is the day-----parents visit the school.a.when which

问题描述:

Open Day is the day-----parents visit the school.a.when which
选什么,请说明缘由,

when
定语从句,先行词是the day,而定语从句是主谓宾都完整:parents(主语) visit(谓语) the school(宾语).
所以排除which,一般在宾语从句当主语或宾语.
说明定语从句缺时间状语,引导词用when.
意义:开放日是家长可以参观学校的日子.