一：被强调成分是主语，who/that之后的谓语动词应该在人称和数上与原句中的主语保持一致。如：It is the soldiers who are our most lovable persons in the world.
二：被强调部分既包括人又包括物，用that不用who。如：It was the things and people that they remembered that they were talking about.
三：即使被强调成分是句子中的时间状语、地点状语、原因状语等，也不能用when，where，because，要用 that。如：It was in front of the bank that the old lady was robbed.
