指示代词的几点用法说明
1. 指示代词的基本用法
指示代词包括this, that, these, those等，它们在句中既可用作代词，也可用作形容词。一般说来，this, these表“近指”，，而that, those则“远指”。
2. 指示代词指上文还是指下文
指上文提到的事多用that，有时用this，指下文的事只能用this。如：
—He was nearly drowned once.
—When was ________?
—________was in 1998 when he was in middle school.
A. that; It B. this; This C. this; It D. that; This
答案是A。指上文提到的事多用that，it指时间。
3. 电话用语中的指示代词
在电话用语中指自己用this，指对方用that，不用I或you。如：
“Who’s that?” “This is Mary speaking.”“你是哪位？”“我是玛丽。”
4. 指示代词受定语从句的修饰
指示代词that, those后可接定语从句，一般说来，that后接which引导的定语从句，those后接who引导的定语从句。如：
They say the only real knowledge is that which can be measured. 据说唯一真实的知识是可以检验的知识。
Only those who had booked in advance were allowed in. 只有那些预先订票的人可以进去。
5. 指示代词用作替代词
that, those有时可用作替代词，用以替代前面提到过的人或事物。如：
My seat is next to that of the mayor. 我的座位在市长座位旁边。
Waves of red light are about twice as long as those of blue light. 红色光线的波长约为蓝色波长的两倍。