Final answer:
Matthew Granger breached his duty of care primarily through negligence.
Step-by-step explanation:
Matthew Granger breached his duty of care primarily through negligence. Negligence refers to the failure to exercise the level of care and diligence expected in a particular role or position. In this case, Matthew's failure to attend board meetings, stay updated on company developments, and review financial records demonstrates a lack of care and diligence. This breach of duty can have negative consequences for the company and its shareholders.