做代词时，one可代替不可数名词和可数名词单数,ones代替可数名词复数替代词one/ones常常用来代替上文提到过的名词,以避免重复。例如:I don5t like this book.Show me a more interesting one.There are good films as well as bad ones.但在具体使用的过程中,同学们常常会出一些错。下面拟通过一些实例分析,以说明替代词one/ones的用法。1.忌用one/ones替代不可数名词。遇到不可数名词往往采用“重复使用”或“省略”的方法。例如:误:I prefer white coffee to black one.正:I prefer white coffee to black/black coffee.2.忌把one与不定冠词a直接连用,但前面有形容词修饰时,其前方可加a/an。例如:误:Can you play the violin?There is a one in the room.正:Can you play the violin?There is one/a new one in the room.3.忌把one/ones与形容词性物主代词直接连用,在两者之间插入适当的形容词后方可...ones必须和形容词连用。如果替代的名词时无形容词在前，则用some, any，而不用ones。 Have you bought any rulers? Yes，I 've bought some.

严格地抠语法算不对，poorsleep做名词，students和poorsleep不是一类没有可比性，所以不能直接用be连接。可以改为infact,manystudentswhoareinattentiveinclasshavepoorsleep.如果要用ones，可以改为infact,manystudentswhoareinattentiveinclassareoneswithpoorsleep.