The Empire State Building, the Sears Tower, the Canadian National Tower - each of these structures was the tallest in the world at the time they were (Option D) built.
<h3>What is sentence correction?</h3>
Sentence correction or sentence improvement is a type of grammatical practice where a sentence is given with a word or a phrase that requires grammatical changes or improvement.
Now,
- Here, we are talking about each of the mentioned structures.
- By grammar, everything used for them must be singular.
- But as mentioned in the sentence in part D, the plurals "they were" are used, which is the faulty part of the sentence.
Hence, Option D is the correct part that needs correction; the correction would be: "it was built."
To learn more about sentence correction, refer to the link: brainly.com/question/14632568
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