## Core Concept
In starvation, the body's primary goal is to maintain blood glucose levels and provide energy to vital organs. During this state, glucose utilization shifts among various tissues to prioritize those that are glucose-dependent.

## Why the Correct Answer is Right
The correct answer, **brain**, is right because the brain primarily relies on glucose as its metabolic fuel under normal conditions and even during starvation. The brain lacks significant stores of glucose and depends almost exclusively on a continuous supply of glucose from the blood. Even in starvation, when the body begins to break down fat for energy, the brain continues to use glucose.

## Why Each Wrong Option is Incorrect
- **Option A: Liver** - The liver plays a crucial role in glucose metabolism, including gluconeogenesis and glycogen storage. However, it does not primarily utilize glucose as a fuel source; instead, it produces glucose for other tissues.
- **Option B: Skeletal muscle** - Skeletal muscle can use glucose, but during starvation, it shifts towards using fatty acids as a primary energy source. It can also store glucose as glycogen, but its primary fuel during fasting/starvation is not glucose.
- **Option C: Adipose tissue** - Adipose tissue stores fat and releases fatty acids during starvation. It does not primarily utilize glucose for its energy needs; instead, it relies on fatty acids.

## Clinical Pearl / High-Yield Fact
A key point to remember is that during starvation, after initial depletion of glycogen stores (which lasts about 24 hours), the body begins to break down fat for energy. However, the brain continues to rely heavily on glucose. After a few days of fasting/starvation, the brain can adapt to use ketone bodies as an additional fuel source, but glucose remains essential.

## Correct Answer: D. brain