Steroid is

Options

A. Cholesterol
B. Thyroxine
C. Vitamin A
D. Fatty acid ester.

Answer

### Step-by-Step Solution:

1. **Definition of Steroid**: A steroid is a type of organic compound that is characterized by a specific molecular structure. It is derived from cholesterol.

2. **Cholesterol as a Precursor**: Cholesterol is a sterol, which is a type of steroid. It plays a crucial role in the structure of cell membranes and serves as a precursor for the synthesis of steroid hormones.

3. **Types of Steroids**: Steroids can be classified into different categories, including sex hormones (like testosterone and estrogen), corticosteroids (like cortisol), and anabolic steroids.

4. **Hormonal Function**: Steroids, particularly steroid hormones, are involved in various physiological processes, including metabolism, immune response, and regulation of inflammation.

5. **Examples of Steroids**: Some common examples of steroids include testosterone, estrogen, progesterone, and cortisol. Thyroxine (T3 and T4) is a hormone but is not classified as a steroid; it is derived from the amino acid tyrosine.

6. **Distinction from Other Compounds**: It is important to differentiate steroids from other compounds such as vitamins (like vitamin A) and fatty acids, which do not share the same structural characteristics as steroids.