Which Sentence Will Define the Dissolution Rate

Which sentence will define the Dissolution rate?

A) Amount of solid substrate that goes into solution under constant time
B) Amount of solid substrate that goes into solution under constant time under standard temperature
C) Amount of solid substrate that goes into solution under constant time under standard temperature, pH, and pressure
D) Amount of solid substrate that goes into solution under constant time under standard temperature, pH, solvent composition and constant surface area