Refer to the figure.
Describe an experiment to test the hypothesis that PK2 is a key clock messenger responsible for regulating circadian behaviors. Base your experiment on the results shown below, which show activity levels for rats in two treatment groups. Explain your predictions if the hypothesis is supported, and if the hypothesis is not supported. Note that rats are usually active during the nighttime, and PK2 production is normally high during the daytime and low during the nighttime.