He wanted to know "why I was going to school.", this sentence has the correct use of punctuation, as it has the correct use of quotation mark and full stop in the sentence.
What is Punctuation?
Punctuation are the marks used in between of the sentence to break or pause the sentence, and to give clear meaning of the sentence. Some punctuation mark are comma, colon, quotation mark, hyphen etc.
In the above sentence the punctuation, quotation mark has been used correctly. In the rest of the sentences, question mark, comma etc are not placed correctly.
Therefore, option, D, He wanted to know "why I was going to school.", is correct.
Learn more about, Punctuation, here,
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