You need to create a business process flow (BPF) that spans multiple entities.
Which of the following statements is true?
A. You can use entities that have N:N relationships.
B. The same entity cannot be used twice.
C. Relationships must exist between entities.
D. You can include a maximum of five entities.
Answer is : D
https://docs.microsoft.com/en-us/dynamics365/customer-engagement/customize/business-process-flows-overview#multiple-entities-in-business-process-flows