In your opinion, what does the target market see or prefer the most? TV, radio or newsletters?

The medium most preferred will vary based on the particular demographic you are looking at. The product itself will also determine the best medium to use. However, I would say radio is the most accessible across all demographics but its lack of visual input limits its effectiveness depending on the message you need to put across.

Based on the above and with a well defined product and/or target market you will be able to determine which medium to use.

In my opinion, All 3 of them.

TV, safely based on the fact that it is the most popular, vastly accessed and easily reachable of all the three.

Whatever may be your demographic, your target market would watch a certain amount of television and most importantly, you can display tangible benefits so the visaul content can show the product in most attractive manner.

It should be TV because of overall audio- visual impact

All of them , and direct marketing is important also 

Thanks for invitation