Agreed in thinking answer is B
"A random data extension splits up subscribers from a selected standard data extension and places the subscribers into new data extensions in Marketing Cloud Email Studio. You can create as many as 12 data extensions at a time."

https://help.salesforce.com/s/articleView?id=sf.mc_es_create_random_de.htm&type=5

C and D is wrong, in Automation Studio there is no random split activity, in Journey Builder exist but we can split up to 10 groups not 11. The proper answer is Random Data Extension with Email Studio.

C - https://help.salesforce.com/s/articleView?id=sf.mc_jb_split_journey_contacts_at_random.htm&type=5