The correct option is B several books
Option C is the correct answer. The verb are lying establish that the work in the sentence is done by the phrase several books, they are being talked about in the sentence. Option A constitutes the adverbial clause of place providing a setting for the events occurring in the sentence. Option B, being part of the clause, cannot be a subject. Option D, them, is the object of the verb written, being spoken about the subject several books. Thus, Options A,B and D are all incorrect.