Based on the transcript, the thing which broadcasting the story through the medium of radio allow Welles to do is D. Announce the closing of the radio station
This refers to the broadcast that is done by an On-Air Personality that tells events to a group of listeners on the radio.
Hence, we can see that based on the given text, the speaker sends a radio message and this enables him to announce the closing of the radio station to his listeners.
This is because, through his radio broadcast, he was able to show that the threat of an alien invasion was real which made him a reliable narrator and the people believed him as he announced the closing of the radio station.
Read more about radio messages here:
https://brainly.com/question/14029881
#SPJ1