**Core Concept**
Laplace's law relates to the **pressure** and **wall tension** in a cylindrical structure, such as a blood vessel. This law is crucial in understanding **vascular physiology** and **cardiovascular medicine**. It describes the relationship between the **radius** of the cylinder, the **wall tension**, and the **internal pressure**.

**Why the Correct Answer is Right**
The correct formula for Laplace's law in a cylinder is given by the equation: **T = PR**, where **T** is the wall tension, **P** is the internal pressure, and **R** is the radius of the cylinder. This equation shows that the wall tension is directly proportional to the internal pressure and the radius of the cylinder.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately represent the relationship between wall tension, internal pressure, and radius in a cylindrical structure.
**Option B:** This option is also incorrect as it misrepresents the formula for Laplace's law in a cylinder.
**Option D:** This option is incorrect because it does not correctly express the relationship between the variables.

**Clinical Pearl / High-Yield Fact**
Laplace's law has significant implications in **cardiovascular medicine**, particularly in understanding **hypertension** and **aneurysm formation**. Remember that as the radius of a blood vessel increases, the wall tension also increases, which can lead to vessel rupture if not managed properly.

**Correct Answer:** T = PR