What is the minimum number of certificates?

Your company has an Exchange Server 2019 organization that has servers deployed in two Active Directory forests named adatum.com and contoso.com. The organization contains five Mailbox servers and two Edge Transport servers. You deploy Microsoft 365 and configure Exchange Online.

You plan to configure hybrid mail transport.

You need to identify the number of third-party CA certificates that must be used in the deployment.

What is the minimum number of certificates?
A . 1
B . 2
C . 4
D . 5

Answer: A