Answer:
Option 3rd is correct.
Step-by-step explanation:
Given: Number of books = 5
We have to find number ways in which 5 books can be arranged on a shelf.
We have 5 places to arrange the books.
Consider,
Place 1 for that we have 5 options to place a book.
⇒ Number of ways for place 1 = 5
Now, Place 2 for that we have 4 options as 1 books is already placed on place 1.
⇒ Number of ways for place 2 = 4
Now, Place 3 for that we have 3 options as 2 books is already placed on place 1 & 2.
⇒ Number of ways for place 3 = 3
Now, Place 4 for that we have 2 options as 3 books is already placed on place 1 , 2 & 3.
⇒ Number of ways for place 4 = 2
Lastly, Place 5 for that we have 1 options as 4 books is already placed on before.
⇒ Number of ways for place 5 = 1
Total Number of ways = 5 × 4 × 3 × 2 × 1 = 120
Therefore, Option 3rd is correct.
