Final answer:
Max Harper, diagnosed with Intellectual Disability, shows signs of depression option (b), as indicated by his sadness and isolation after starting a new high school.
Step-by-step explanation:
Max Harper, who has been diagnosed with mild Intellectual Disability, is experiencing challenges in his new high school, feeling sad and isolating himself from his family. These symptoms suggest he is not dealing with social anxiety or ADHD specifically and that he is certainly not adjusting well to his new environment.
Instead, Max may be exhibiting signs of depression, which can manifest through sadness and withdrawal from social interactions, both of which Max is experiencing. This is not uncommon, as there are cases where learning disabilities coexist with other disorders including mental health issues.
Furthermore, Intellectual Disability, as described in the DSM-5, entails both challenges in intellectual functioning as well as adaptive behaviors, which can impact social integration.