In Adjacent Rocks That Show a Gradual Increase in Metamorphic

Multiple Choice

In adjacent rocks that show a gradual increase in metamorphic intensity, the first appearance of a particular index mineral indicates

A) the location of the minimum pressure and temperature conditions needed for the formation of that mineral.
B) the location of the maximum pressure and temperature conditions needed for the formation of that mineral.
C) the rocks formed under the same broad conditions of temperature and pressure.
D) the location on Bowen's reaction series where that mineral is in equilibrium.