Final answer:
Independent companies that assist exclusively in the purchase of radio and television time are known as media specialist companies. They play a critical role in navigating the consolidated media marketplace and securing advertising opportunities for targeted narrowcasting.
Step-by-step explanation:
Independent companies that exclusively help in the purchase of radio and television time are known as media specialist companies. These companies focus on planning and buying media space or time for advertising campaigns. Their specialized knowledge in rates, times, and media platforms allows advertisers to effectively place their ads, reaching target audiences more efficiently. With the current climate of media consolidation, where a few firms dominate the media marketplace, and the move from mass broadcasting to narrowcasting, the role of media specialist companies is increasingly important in navigating and securing strategic advertising opportunities.