half of the students 还是one-second of the students

题目

half of the students 还是one-second of the students
_____ of the students attend interest clubs after class.
a.one-second b.half
想问问为什么

答案

为什么.虽然我没有见过one-second这种说法,但是half好像也不用of呀.
不过我还是找到答案了.
half的用法与all和both相同,既可用作形容词（或称限定词）修饰名词,如 half the year,half the work,half the fruit,亦可用作不定代词,受of短语修饰,如：half of the work,half of the year,half of the fruit.这两种表达形式在意义上没有明显的区别.
可以当做不定代词这里.
one-second是没有这种说法的.