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

Explanation:

A proactive message is any message sent by a bot that isn’t in response to a request from a user. Sending a proactive message is different from sending a regular message. There’s no active turnContext to use for a reply. You must create the conversation before sending the message.

Reference: https://docs.microsoft.com/en-us/microsoftteams/platform/bots/how-to/conversations/send-proactive-messages