一般疑问句如果是如下句式:Is this your mother's friend?回答为:Yes, it is.而一般疑问句如果提问变为:Is she his wife?回答则为:Yes, she is.为何this/that的回答时的人称代词是it,而直接的在疑问句中提到是she/he,回答是she/he呢?