一段名詞子句的英文文法

原文
Question:
My son, a third-grader, has difficulty spelling. However, he does great on his weekly
spelling tests—all “A” grades. Can you explain this? How can I help him?
– No Speller

Answer:
The words that children need to learn how to spell are the ones that they use in
their daily writing. It is quite possible that the words your son is learning on the weekly spelling tests simply aren’t the ones he needs the most for his daily work.

有兩個問題

一、the ones的意思是？什麼時候可以用？
二、Answer的第一段我知道 The words are the ones，夾在中間的是名詞子句。
但我看不懂這個第二段的文法結構，possible後面是名詞子句，但是又接了
your son is ...，接著又有 spelling tests simply ，後面又接著 aren't 不知道是
延續前面的哪一個字？ 搞不太清楚。

（It is quite possible that the words your son is learning on the weekly spelling tests
simply aren’t the ones he needs the most for his daily work.）