The correct answer is A. silica.
The amount of silica found in the magma determines the viscosity. The higher the silica in magma, the higher the viscosity of a magma. So the correct answer is silica. It is not among the other choices.
The difference is just 1 mph. Winds 73 mph or less is a storm and 74 mph or more is a hurricane.
Approximately 71% of Earth's surface is covered by water.
