Each time a user invokes one of your app's slash commands, a request is dispatched...

Slack's response_url provides a temporary callback mechanism that lets an application send additional responses after receiving a slash command or supported interactive-action payload. Current Slack documentation specifies that the URL can be used up to five times within 30 minutes after the application receives the original payload. That makes B the precise platform restriction. A response_url does not require the app to attach a bot or user OAuth token. Slack treats the URL itself as an authorized response pathway associated with the originating interaction. It can therefore bypass ordinary channel posting permissions for that response context. Option C is incorrect because global shortcuts do not inherently provide a response_url; their primary payload contains a trigger_id, which can be used to open a modal. Option A is also incorrect because interaction responses can modify or replace originating messages where the interaction type supports such behavior. If an app needs to communicate after the 30-minute response window or after exhausting the permitted responses, it should use standard messaging APIs such as chat.postMessage. This maps directly to Design the Interactive Flow of Your App, particularly slash commands, interaction acknowledgments, and asynchronous responses.