In this question, read each sentence to find out whether there is any error in it. If there is no error; the answer is "no error".(Ignore errors of punctuation, if any.)
There are two scores of books
which are lying
unused in the library.
When a quantity is given before 'score' like '2' or '5' etc, 'score' is not used in the plural form. Hence, we would use 'score' in place of 'scores' in the given sentence.