Final answer:
Social media is the best channel for promoting a mountain bike due to its cost-effectiveness, demographic targeting capabilities, and interactive nature, which surpasses the reach of newspapers, radio, or even television.
The correct answer is B.
Step-by-step explanation:
The best media channel for promoting a mountain bike would be social media. This choice is primarily due to the demographic targeting capabilities and virality potential that social media brings to marketing. Unlike television, which is more costly and generally less targeted, or newspapers and radio, which have declined in reach and effectiveness particularly among younger audiences, social media offers a platform where a targeted, dedicated, and interactive audience can be reached, including those with an interest in outdoor activities such as mountain biking. The strategies for promotion on social media also tend to be more cost-effective, and the platform provides opportunities for sharing and engagement that other media channels cannot match.