In the following sentence, four words or phrases have been underlined. One of…

The correct answer is Option D (that was). The sentence contains a subject-verb agreement error in the relative clause. The phrase 'one of the five books' indicates that there are multiple books, making 'books' a plural noun. Consequently, the verb in the relative clause modifying 'books' must also be plural. Therefore, 'that was' is incorrect and should be changed to 'that were'. Options A ('one of the'), B ('This'), and C ('at') are grammatically correct in this context. 'One of the' correctly introduces a plural noun phrase, 'This' serves as an appropriate demonstrative pronoun for the singular subject 'one', and 'at' is the correct preposition to indicate location. The error lies solely in using the singular verb 'was' instead of the plural 'were'.