What is the likely most cause of these results?

A 17-year-old boy with a 10-year history of type 1 diabetes mellitus was admitted with

diabetic ketoacidosis after a night of binge drinking.

He was treated appropriately with a fixed-rate intravenous insulin infusion and intravenous sodium chloride 0.9%.

Twenty-four hours after admission, he was eating and drinking normally. He was taking his usual doses of subcutaneous insulin and his urinary ketones were undetectable.

Investigations (6 hours previously):

venous blood gases, breathing air:

PO25.6 kPa

PCO23.8 kPa

pH7.29

bicarbonate16 mmol/L

base excessC1 mmol/L

lactate1.1 mmol/L

What is the likely most cause of these results?
A . alcohol toxicity
B . concurrent aspirin ingestion
C . continued ketonaemia
D . hyperchloraemia
E . hyporeninaemic hypoaldosteronism