答案：B

本题考查非谓语动词。去掉It was…that后剩下的部分为______ the president's speech the secretary spent the whole morning at home，调整结构后是the secretary spent the whole morning at home ______ the president's speech。结合选项可知句意是：秘书花了整个早上在家为总统准备演讲。由此判断考查的是spend time （in）doing sth句型。