Question

which phases change are occurring at point b?
melting and freezing
freezing and boiling
vaporization and condensation
condensation and freezing

Explanation:

Phase changes are physical processes where a substance changes from one state of matter to another. At point B (assuming it's at the melting - freezing plateau in a phase - change diagram), melting (solid to liquid) and freezing (liquid to solid) occur simultaneously when the system is in equilibrium. Freezing and boiling involve different temperature ranges. Vaporization (liquid to gas) and condensation (gas to liquid) occur at higher temperatures (boiling point). Condensation and freezing also involve different phase - transition temperatures.

Answer:

Melting and freezing