Final answer:
The best explanation for the variance in social media usage among different age groups is the greater fluency younger people have with new technology, making option B the correct answer.
Step-by-step explanation:
The difference in social media usage between older adults and younger individuals is best explained by option B: younger people tend to be more fluent in new technology.
This fluency allows them to navigate, engage with, and adopt social media platforms more readily. Additionally, social media platforms cater to younger demographics with the use of features that appeal to their communication styles and lifestyle.
It's not accurate to say that older people reject everything new in society or that they don't need social media because they have solid friends. Moreover, the economic argument that younger people have the most to spend on devices for social media does not fully explain the differences in usage patterns. Therefore, the mentioned correct option in the final answer is B.