Biology

The correct answer is B.different sounds.

In this experiment, Tiffany is testing how fast Hayden reacts to different sounds. The independent variable is the factor that Tiffany is changing or manipulating in the experiment to observe its effect on Hayden's reaction time. In this case, the different sounds are what Tiffany is varying.

Here’s why the other options are not correct:

A.How fast Hayden reacted: This is the dependent variable, as it is the outcome that Tiffany is measuring in respons...