Which of the following conditions don’t allow to remove a product or price book?

Answer options:

A.If the product is not active
B.If the product or price book is associated with an approval process
C.If the product or price book has a pending workflow action
D.If the price book is not active

Correct Answer: B and C 
You cannot remove a product or price book if the product or price book is associated with an approval process or if the product or price book has a pending workflow action. 
Options A and D are incorrect because the product and price book can be removed if they are not active and they are not linked to any process. 
Reference: 

https://help.salesforce.com/articleView?id=products_del.htm&type=5