A Salesforce admin created a custom object called Applications and a custom report type for it, and he set it as the primary object. What will happen if the Applications object gets deleted?

Answer options:

A.The custom report type will not be affected
B.The custom report type and any report created through it will be hidden, inactivated or disabled
C.The custom report type will remain accessible, but the reports created through it will be deleted
D.The custom report type will be deleted but the reports created through it will be accessible

Correct Answer: B 
If the custom object gets deleted, Salesforce either hides or inactivated or disables the custom report types or the custom reports related to it. 
Option A is incorrect because the custom report type will be affected when the custom object is deleted 
Option C is incorrect because the custom report type will not be accessible once the custom object is deleted 
Option D is incorrect because the custom reports will not be accessible once the custom object is deleted 
Reference: 

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