**Core Concept**
The patch clamp technique is a method used to study the electrical properties of single ion channels in cell membranes. It allows researchers to record the current flow across individual channels, providing valuable insights into their function and regulation.

**Why the Correct Answer is Right**
The patch clamp technique works by forming a high-resistance seal between a glass electrode and the cell membrane, creating a small "patch" of membrane that can be studied in isolation. This seal is achieved using a specialized electrode and a gentle suction system. Once the seal is formed, the electrode can be used to measure the current flow across individual ion channels, allowing researchers to study their properties and behavior in detail. The patch clamp technique is particularly useful for studying channels that are difficult to study using other methods, such as those that are present in low numbers or have complex regulatory mechanisms.

**Why Each Wrong Option is Incorrect**
**Option B:** Voltage Clamp is a technique used to study the electrical properties of cells or tissues by holding the membrane potential at a fixed value and measuring the resulting current flow. While it is a powerful tool for studying cellular electrophysiology, it is not used to study current flow across individual channels.

**Option C:** Iontophoresis is a technique used to deliver charged molecules across cell membranes using an electric field. It is often used to study the movement of ions or small molecules across the membrane, but it is not used to study current flow across individual channels.

**Option D:** Galvanometry is a technique used to measure the flow of electric current in a circuit. While it is related to the study of electrical properties, it is not used to study current flow across individual channels in cell membranes.

**Clinical Pearl / High-Yield Fact**
The patch clamp technique was awarded the Nobel Prize in Physiology or Medicine in 1991 for its discovery and development. It has revolutionized our understanding of ion channel function and regulation and has had a major impact on the field of cellular physiology.

**Correct Answer:**
✓ Correct Answer: A. Patch clamp