I'm working my way through The Blue Book of Grammar and Punctuation, and I came across a difficulty.
In one of the quizzes, the book asks you to identify the subjects and verbs in sentences, and correct disagreements where necessary. Here is one such sentence:
Her attitude is one of the things that's different.
I incorrectly viewed one as a subject in the sentence above, which caused me to miss that things is actually the subject and so the verb should be conjugated are, and the sentence constructed thus:
Her attitude is one of the things that are different.
With me? I'm not 100% clear here why things is the subject and not one, but okay. I understand close enough.
Then I came to this explanation in the section on pronouns. The rule is copied to give context to the example and its explication.
Rule 5. The pronouns who, that, and which become singular or plural depending on the subject. If the subject is singular, use a singular verb. If it is plural, use a plural verb.
Example: He is the only one of those men who is always on time. The word who refers to one. Therefore, use the singular verb is.
Here is where my confusion truly enters the picture. If who as a pronoun is referring to one in this sentence, then one is the subject (as is He). If one is the subject in this sentence, why is it not the subject in the previous sentence?
Thank you for your help! Let me know if I need to clarify my question.