**Core Concept**
Steroids are lipid-soluble hormones that require specific transport mechanisms to enter cells, as they are not actively transported across the cell membrane. This concept is crucial in understanding the regulation of steroid hormone action within the body.

**Why the Correct Answer is Right**
The correct answer is facilitated diffusion, which is a type of passive transport. Steroids can diffuse through the lipid bilayer of the cell membrane due to their hydrophobic nature. However, this process is facilitated by specific steroid-binding proteins, such as steroid carrier proteins, which help to increase the efficiency of steroid entry into the cell. Once inside the cell, steroids can bind to specific receptors, leading to the regulation of gene expression.

**Why Each Wrong Option is Incorrect**
**Option A:** Active transport is incorrect because it requires energy expenditure, which is not necessary for the entry of steroids into cells. While some steroid transport mechanisms may involve energy-dependent processes, facilitated diffusion is the primary mechanism for steroid entry.
**Option B:** Endocytosis is incorrect because it involves the engulfment of particles or molecules by the cell membrane, which is not relevant to the entry of steroids into cells. Steroids can diffuse directly through the cell membrane, eliminating the need for endocytosis.
**Option C:** Pinocytosis is incorrect because it is a type of endocytosis that involves the uptake of fluids and dissolved substances by the cell membrane, which is not relevant to the entry of steroids into cells.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the transport of steroids into cells is a critical step in their action, and alterations in this process can lead to changes in steroid hormone levels and function. For example, certain genetic disorders, such as familial hypercholesterolemia, can affect the transport of cholesterol into cells, leading to elevated cholesterol levels.

**Correct Answer:** C. Facilitated diffusion.