正常的说,应该是：whom I should speak with
或者：who I should speak with
“谁” who （主格） whom（宾格）,这里最正确应该用宾格 whom,但是 习惯上,用who的人也很多,就默认正确了.
who .作为宾语从句,who 后一定要用 陈述语序,所以一定要是 I should ,一定不可以是 should I
C 选项中,with 提前了,是因为：
关系代词whom或which在定语从句中作介词宾语时,介词可放在后面,也可提前构成“介词＋关系代词whom(先行词指人)/which(先行词指物)”引导定语从句.
例如： This is the girl whom I borrowed a book from.
=This is the girl from whom I borrowed a book.这就是我向她借书的那个女孩.
Is this the room which he once lived in?
=Is this the room in which he once lived?这是他曾经住过的房子吗?