An 16-year-old man presents with polyuria and polydipsia. Which of the following may confirm the diagnosis of diabetes mellitus? 1) A random plasma glucose of >7.5 mmol/L 2) A finding of 3+ ketonuria 3) An HbA1c of 7.0% 4) A fasting plasma glucose of 7.5 mmol/L 5) An abnormal glucose tolerance test