System Data Time (min) Mass of System 1 Mass of System 2
0 21.33 21.35
1 21.30 21.35
2 21.25 21.35
3 20.97 21.35
4 20.93 21.36
6 20.90 21.35

The figure above shows two different systems. Each system contains a flask holding an unknown liquid at room temperature. Their masses are recorded on a digital balance at 0, 1, 2, 3, 4, & 5 minutes. The corresponding masses are recording in the data table above. Which uncontrolled variable most likely explains the reduction in mass in System 1?

A) the liquid is evaporating
B) digital balance error in system 1
C) the liquid is dissolving inside the flask
D) water is condensing on the outside of the flask