What is the process where frost forms

Sublimation

Explanation:
Frost forms when an outside surface cools past the dew point. The dew point is the point where the air gets so cold, the water vapor in the atmosphere turns into liquid. As cool air collects in valleys, frost forms. Frost usually forms at night, when the air temperature is cooler.

I hope this helped! :)

Rn in the right answer

Answer trigonal pyramidal;