What is the purpose of report type?

Answer options:

A.It provides more information on who can access the report
B.It provides the date range for the report
C.It adds more filters in your report
D.It shows the fields and the records that can be used while creating a report

Correct Answer: D 
Report Type shows the fields and the records that can be used while creating a report within Salesforce. It works through displaying the connection between the primary object and its related objects. 
Option A is incorrect because report type doesn’t provide any information about who can access the report 
Option B is incorrect because report type doesn’t show the data range for a report 
Option D is incorrect because report type is not used for adding any filter in a report 

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