Context: The passage below describes an experiment.

After a severe winter storm, Liam's driveway was covered with ice. He read that salt makes ice melt at a lower temperature. Before covering his entire driveway with salt, he wanted to know if adding salt could actually help melt ice in the freezing outdoor temperatures.
Liam weighed twenty ice cubes. He sprinkled salt on half of the ice cubes and left the other half unsalted. He placed all the ice cubes outside. One hour later, Liam quickly dried each ice cube and reweighed it to see how much it had melted.
Figure: an icy sidewalk.
In this experiment, which were part of a control group?
A. the unsalted ice cubes
B. the salted ice cubes
Identify the correct choice from the options below and respond with the letter of the correct option.

A