Answer:
D.
Step-by-step explanation:
1 bookshelf have option of 8 books where, only one book can be kept
2 bookshelf has 7 options of books as ( 8-1=7, where 1 is already kept in bookshelf, than same goes on till last shelf where it got 3 options of book in the last place,
therefore, total no. of ways = ( 8*7*6*5*4*3)
= 20160 ways
