What is required for the Teams app to send a proactive message to the users?

You are developing a Microsoft Teams app that will use an Azure function to send scheduled messages from a bot to users .

What is required for the Teams app to send a proactive message to the users?
A . The bot must be approved in Azure Active Directory (Azure AD).
B . The bot must be granted admin access to the users.
C . The Teams app must be added for each user.
D . The users must send at least one message to the bot.

Answer: D