Question

the passage below describes an experiment.
an icy sidewalk
after a severe winter storm, rons 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. ron weighed twelve ice cubes. he sprinkled one teaspoon of salt on four of the ice cubes and two teaspoons of salt on four others. he left the remaining four unsalted. he placed all the ice cubes outside. one hour later, ron quickly dried each ice cube and reweighed it to see how much it had melted.
in this experiment, the unsalted ice cubes were part of ______________.
a control group
an experimental group

Explanation:

In experimental design, a control group serves as a baseline for comparison, remaining untreated (or receiving no variable being tested) to isolate the effect of the independent variable. Here, the salt amount is the tested variable, so unsalted ice cubes are the control to compare melted amounts against salted ones.

Answer:

a control group