Final answer:
The term 'dry magma' typically refers to magma that lacks substantial volatile components like water vapor but isn't entirely free of gases. The correct answer is d) Is high in silica content, as dry magmas tend to be silicic or felsic with high silica content affecting their viscosity and gas content.
Step-by-step explanation:
When referring to dry magma, which is also known as gas magma, it is important to understand that it contains different elements and compounds, including gases. However, if gas magma is characterized as being 'dry,' that typically indicates a lack of substantial volatile components such as water vapor.
This can lead one to think that answer b) Contains no gases would be correct; however, this is somewhat misleading, as even dry magma usually contains some gases, just in smaller amounts. When considering the characteristics of magma high in silica content, which tends to be more viscous, it does not directly relate to the presence of gas but rather to the chemical composition and physical properties of the magma.
Therefore, the correct answer is d) Is high in silica content. The viscosity of silicic or felsic magma (high in silica) influences the gas content of the magma, with higher viscosity trapping more gas and lower viscosity allowing gas to escape more easily. Hence, dry magma or gas-poor magma can still have a high silica content, significantly affecting its physical characteristics.