Answer:
Option C, The mass of water is equal to the mass of water vapor produced.
Step-by-step explanation:
Josie observed that when she is boiling the water, it completely turns into water vapor/steam. From this she might have concluded that since it is the liquid water that has evaporated completely, therefore the mass of this water in gaseous phase must be equal to mass of water in liquid phase as only the phase of the substance has changed and not the substance itself. A steam or evaporated water is still water just like liquid water but is gaseous phase.
Hence , option C is correct