上面第一句为特殊疑问句,第二句为一般疑问句,它们不能倒过来说成Do you think what he wants? What do you know he wants? 其原则区别是:可以用 yes 或 no 回答者,用一般疑问句的形式(疑问词放在句中,即主句之后),适合这类句型的主句动词通常有 know, hear, ask, tell 等;不能用 yes 或 no 回答者,用特殊疑问句的形式(疑问词放在句首),适合这类句型的主句动词通常有 think, believe, suppose, guess 等:
Where do you suppose he has gone? 你认为他去什么地方了?
Did you ask why he had left so soon? 你问过他为什么那么快就离开了吗?