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.