two thirds 作主语时谓语怎么变化

任何分数表达+ of + 名词 + 动词：句子的谓语动词的数取决于 of 后的名词的形式,而不是分数表达本身的单、复数形式.
看例句体会：
Two-thirds of the earth is covered with water.
Two-thirds of the apple is rotten.
...+ 一个整体/单数、可数名词 + 单数
Two-thirds of the information is wrong.
...+ /u/ + 单数
Two-thirds of the books are on education.
...+ 复数可数名词 + 复数

Two thirds of the work has been done. 名词是不可数，谓语用单数。
Two thirds of the students are in the classroom. 名词是复数，谓语用复数。