Which two actions should an app builder take to accomplish this requirement?

Universal Containers has created the custom objects Candidate and Interview in Salesforce to track candidates and interviews respectively. The company wants to track the total number of interviews a candidate has gone through on the candidate record without writing any code.

Which two actions should an app builder take to accomplish this requirement? (Choose two.)
A . Use a formula field on the Candidate record to show the total number of interviews.
B . Use a roll-up summary field on the Candidate record to show the total number of interviews.
C . Use a master-detail relationship between the Candidate and Interview objects.
D . Use a lookup relationship between the Candidate and Interview objects.

Answer: BC