You are building a bot by using Microsoft Bot Framework.

The question requires enabling the bot to respond to spoken requests with minimal effort. Among the options:

Cortana integration automatically adds speech input/output capabilities to the bot.

Direct Line Speech is another option but requires additional setup and coding, so not the minimal effort solution.

Microsoft Teams is primarily for text-based interactions (though can do voice calls, but not direct bot speech input).

Azure function + Speech would require more development overhead.

Thus, Cortana integration provides the simplest path.