The police were seeking more information to find out _______ the rich man.
who was it that killed
who it was that killed
it was who killed
who was it killed
本题考查特殊疑问句的一般陈述语序与强调句
B选项，句意为“警察正在搜集更多的信息来调查是谁杀死了这个富人”。根据强调句结构应为it was who that killed，再调整语序为who it was that killed。综上，B选项正确。
A选项，不符合强调句的语序，故排除。
C选项，不符合强调句的语序，故排除。
D选项，与强调句的结构不符，故排除。
故正确答案为B项。
