These are some pictures of Beijing ,where is my hometown.这句话

which
定语从句关系代词或关系副词的选择,主要看先行词在从句中所作的成分,Beijing在从句中作主语,所以不能选关系副词where,而选which,而且which可引导非限定性定语从句,本句就是个非限定性定语从句
因为是Beijing在从句中做主语
Where=which in
因为是在这些照片中选一个.