Final answer:
The dependent variable in the scenario of testing hockey goalie masks made of titanium and steel is the changes observed in the masks (C) the cages, in response to being hit by pucks at varying speeds and heights.
Step-by-step explanation:
In the scenario where an experimenter designs two cages for hockey goalie masks, one of titanium and one of steel, and hockey pucks are fired at the masks at different speeds and heights, the dependent variable is the outcome that the experimenter would measure in response to the different conditions applied to the experiment. In this case, it is likely to be the amount of damage or deformation to the masks after being struck by the pucks at various speeds and heights. The dependent variable can be influenced by changes to independent variables, which in this experiment would be the material of the cages (titanium or steel), the speeds, and the heights at which the pucks are fired. Therefore, the correct answer to the question presented is C) the cages, as these are what will be measured and evaluated after the experiment.