Universal Container’s Sales Ops admin wants to create a report that pulls all open customer support cases grouped by severity.What is the best report that can help her to meet this requirement?

Answer options:

A.Tabular
B.Summary
C.Summary and Tabular
D.Matrix

Correct Answer: B 
Summary reports are like tabular reports, but you can group the row of data, view subtotals, and create charts in summary reports. It gives users more option to organize their data. 
Option A is incorrect because in the tabular report you cannot group the data. 
Option C is incorrect because you can’t create Summary and Tabular reports grouped together. 
Option D is incorrect because the Matrix report gives you the ability to group records by column and row and they are considered time-consuming. 
Reference: 

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