代词it和that的用法

it,单数,特指,相当于“the + 单数/不可数名词”；与所指代名词属同一类,而且是同一个。This is my watch; it’s a Swiss one。(《牛津现代高级英汉双解辞典》)。Where is my book?Have you seen it?(同上)以上两句中的it均特指前面所指代名词,和前面所指代名词同类而且是同一个。that的用法that,特指,单数,相当于“the + 单数/不可数名词”,与所指代名词同类,但不同一,具体指哪个取决于其后定语of-短语。例如：My seat was next to _______ of the teacher。A。one B。it C。that D。seat空白处需一代词代替其前可数名词seat,以避免重复。因有后置定语of the teacher,故所需代词为特指,且与所指代名词同类不同一（老师的座位）,故排除A、B、D,答案为C (that)。又如：Nine in ten parents said there were significant differences in their approach to educating their children compared with _______ of their parents。A。those B。one C。both D。that 空白处需一代词代前面名词approach,单数,故排除A、C。因有后置定语of their parents,特指,故排除B。答案为D (that)。