Directions: Fill in the blank with appropriate word from the given options. I listened, but I had no idea what he was ________ about.

Talking is correct because 'talk about' is the correct prepositional verb. Saying cannot be followed by 'about' - you say something directly. Telling would require an object (tell someone about something), not just 'telling about'. Discussing is transitive and doesn't take 'about' - you discuss something, not discuss about something.