Questions: Magma with highest viscosity is also the most prone to... violently erupt contain very little water or gas be the hottest form long, fast moving lava flows

The answer is the first one: violently erupt.

Explanation for each option:

1. Violently erupt: Magma with high viscosity is thick and resistant to flow. This can lead to a buildup of pressure as gases are trapped within the magma. When the pressure becomes too great, it can result in a violent eruption. Therefore, high-viscosity magma is indeed prone to violent eruptions.

2. Contain very little water or gas: High-viscosity magma often contains a significant amount of dissolved gases. These gases contribute to the pressure buildup that can lead to explosive eruptions. Therefore, this option is incorrect.

3. Be the hottest: High-viscosity magma is typically cooler than low-viscosity magma. For example, rhyolitic magma, which is high in viscosity, is cooler than basaltic magma, which is low in viscosity. Therefore, this option is incorrect.

4. Form long, fast moving lava flows: High-viscosity magma does not flow easily, so it is unlikely to form long, fast-moving lava flows. Instead, it tends to create shorter, slower-moving flows or even dome-like structures. Therefore, this option is incorrect.

In summary, high-viscosity magma is most prone to violently erupt due to the buildup of pressure from trapped gases.