句中one和ones（三处）分别是什么词性

请问句中one和ones（三处）分别是什么词性？主语、宾语、定语还是表语？谢谢。

Look at that boy!
Which one? 1
The one wearing a sweater. 2
Which boxes are bigger, these ones or those one? 3

网友三个句子中的one和ones均为名词替代词。替代前面的可数名词以防止重复名词。

which one= which boy

the one = the boy

these ones= these boxes

those ones = those boxes