You are building a flight booking bot by using the Microsoft Bot Framework SDK. The bot will ask users for the departure date. The bot must repeat the question ...

You are building a flight booking bot by using the Microsoft Bot Framework SDK.
The bot will ask users for the departure date. The bot must repeat the question until a valid date is given, or the users cancel the transaction.
Which type of dialog should you use?

A. prompt B. adaptive C. waterfall D. action