According to the last paragraph, what is the main factor...

Câu hỏi: Read the following passage and mark the letter A, B, C, or D to indicate the correct answer to each of the questions from 44 to 50.
There has always been a problem with teachers being from a different generation to their pupils, particularly older educators. But the dominance of digital technology has spread that generation gap even wider, as young people become conversant with mobile digital devices, games and social media that didn't exist when their teachers were growing up. Teachers now face pupils using devices and online systems that they don't use themselves, and don't really understand either. The generation gap is more prevalent than ever, but teachers can bridge that gap if they receive the right guidance with appropriate technology.
Some schools and teachers have particular trouble grasping the role of social media and mobile devices in teenage life. They consider Facebook a threat and warn parents against it at parent-teacher evenings, without realizing that preventing teenagers from using social media like this, or messaging apps such as Snapchat and Instagram, is nearly impossible. Online social media and network gaming are now such an integral part of teenage behavior that any attempt to prize the mobile devices out of the hands of young people is likely to widen the generation gap rather than narrow it.
The generation gap in education isn't just between pupils and teachers – it exists within the staffroom, too. A teaching career can span more than 40 years, and those towards the end of their working life will not have grown up with digital technology, whereas teaching staff in their 20s and 30s could well be "digital natives".
Keeping up with the latest online trend is like a dog chasing its tail; every time you think you've caught up, kids move on. However, it's not beneficial to get fixated on how young people are using social networks that are, in the case of Snapchat, hard for the older generation to understand. The key factor to consider is that today's school students now take for granted that a lot of their communication with their peers will be online, and predominantly using smartphones and other mobile devices. Young people expect their educational experience to be similarly interactive, and partially delivered via these kinds of devices.
(Adapted from https://www.alphr.com/)
According to the last paragraph, what is the main factor to consider in the generation gap between teachers and students?
A. It's hard for the older generation to understand the social networks used by the young.
B. Students get accustomed to communicating with their friends online by smartphones and mobile devices.
C. Teachers should use these social networks to provide education.
D. Students are competing with the latest online trend with their peers.