Final answer:
The communication channel that is likely to have the longest delay in response time is radio communication due to the vast distances involved.
Step-by-step explanation:
The communication channel that is likely to have the longest delay in response time is radio communication.
Radio waves travel at the speed of light, which is the fastest known speed in the universe. However, when communicating with distant planets or civilizations, the vast distances involved can introduce significant delays in response time.
In the given scenario, it takes 35 years for the radio message to reach the planet orbiting the star 35 light-years away. Additionally, it takes 2 years for our governing bodies to decide on a response and another 2 years for their governing bodies to frame a reply. Therefore, the total time from receiving the first message to receiving their reply would be 39 years.