This is the factory (that) we visited yesterday morning and (where) is the one my father worked
选C
原因：
分解句子
1.This is the factory (that) we visited yesterday morning 此句中,we visited 后面缺宾语,关系词应用关系代词which或that
2.This is the factory (where) is the one my father worked 此句中work后缺关系副词where或in which