The correct answers are:
Spending more time online
Matthew started spending lots of time online watching videos about terrorist attacks. This led to him being introduced to radicalisers in an online chat room.
Communicating with an extreme right-wing group
Matthew had been communicating with members of an extreme right-wing group online who were allegedly recruiting people into their organisation and attended a meeting with them. He was being influenced by the extremist group.
Displaying antisocial behaviour
Matthew would demonstrate antisocial behaviour by shouting at non-white people in the street telling them to go home and vandalising their property. He also started voicing his opinions on other races at school making other people feel uncomfortable.
The incorrect answers are:
Joining the army cadets
Although joining the army cadets may seem like a cause for concern, as it suggests wanting to fight in a war, in this case, Matthew simply wanted to follow in his dad's and grandad's footsteps, so there is no cause for concern.
Becoming more independent
Matthew had to become more independent as he became more isolated from his family. Although this may be seen as a potential vulnerability for a young person, leaving them more susceptible to extremist ideology, it has no connection with being radicalised into terrorism in this case.