Which of the following sentences uses the correct subject-verb agreement?

At the party there were no one I knew.

There was many problems with the construction of the house.

One important aspect of the book is its detailed descriptions.

One important aspect of the book is its detailed descriptions.

are you very sure

Yes, I am confident that the sentence "One important aspect of the book is its detailed descriptions" uses the correct subject-verb agreement. The subject "One important aspect" is singular and requires the singular verb "is."