Which of the following is NOT a component of magma?

Magma is a molten rock material found beneath the Earth's surface, and it is composed of several key components. Silica is a fundamental part of magma and significantly influences its properties, including viscosity. Carbon dioxide is often dissolved in magma and can play a role in volcanic eruptions. Water is also an essential component, present in various forms, and contributes to the magma's behavior and the formation of volcanic gases.

While iron is commonly found in many types of rocks and minerals that make up the Earth's crust and mantle, it is not a primary component of magma itself. Instead, iron is often present in mineral forms such as olivine and pyroxene, which may crystallize from the magma as it cools. In contrast, the other components listed are directly involved in the liquid state of magma, making them fundamental to its composition and behavior when below the Earth's surface.