**Core Concept**
Ketoacidosis in diabetes mellitus arises from a deficiency of insulin, leading to uncontrolled lipolysis, increased free fatty acid levels, and accumulation of ketone bodies such as acetoacetate and acetone. This metabolic state is characterized by a shift in hormonal balance, particularly a rise in glucagon relative to insulin, which drives hepatic glucose production and lipolysis.

**Why the Correct Answer is Right**
In diabetic ketoacidosis (DKA), insulin deficiency results in a dramatically increased glucagon-to-insulin ratio. This imbalance stimulates adenylate cyclase, increasing intracellular **cAMP** in liver and adipose cells, which enhances lipolysis and gluconeogenesis. The lack of insulin also leads to elevated blood glucose due to reduced glucose uptake by tissues. Free fatty acids are released and oxidized, producing ketone bodies as an energy source, contributing to metabolic acidosis. Thus, increased glucagon/insulin ratio, elevated cAMP, and high blood glucose are all hallmark features of DKA.

**Why Each Wrong Option is Incorrect**
Option B: While decreased insulin and increased free fatty acids are correct, stating that free fatty acids are "equivalent to blood glucose" is misleading. Free fatty acids are not metabolically equivalent to glucose; they are used as fuel and do not directly substitute for glucose in energy metabolism.
Option C: The claim that free fatty acids are "not equivalent to blood glucose" is incorrect because the statement lacks clinical relevance—fatty acids are not interchangeable with glucose in metabolic function.
Option D: Elevated insulin contradicts DKA pathophysiology; insulin is low, not high. Also, free fatty acids are not equivalent to glucose, making this option factually and logically flawed.

**Clinical Pearl / High-Yield Fact**
In DKA, **insulin deficiency** is the root cause, leading to a **glucagon/insulin ratio increase**, which drives hyperglycemia, ketogenesis, and metabolic acidosis. Always remember: **no insulin = no suppression of glucagon = increased cAMP = ketone production**.

✓ Correct Answer: A. Increase in glucagon/insulin ratio, increased CAMP and increased blood glucose