It s difficult to say-----this portrait was painted by 横线处可以填that吗为什么呢
问题描述：
It s difficult to say-----this portrait was painted by 横线处可以填that吗为什么呢
如果填who 那么that不是可以替换who吗。
答
不能,应该填WHO
因为从句后面是was painted by,少了人（by什么?不知道）,所以应该填who