A & D

Answer should be A & D

I think A&D too:

https://help.salesforce.com/s/articleView?id=000386702&type=1

"If the default Max Roll-Up Summary Field limit per object (increased from 10 to 25 in the Winter '16 release) isn't sufficient for your organization's business processes, you can use these steps:


Request increase for Max Roll-Up Summary Field limit
Have your system administrator create a Support Case with the Feature Activations & Limits Team.


Once your case has been created, our Support team will review and action it accordingly.

If your limit has been increased to the maximum amount, and the issue still persists, please try deleting previous unused custom fields."

Answer : a & d

C is wrong. AVG is not available. D is wrong as upto 40 rollup summaries can be made for a obj. Only A is correct here.