A Medical Journal Published the Results of an Experiment on Insomnia

A medical journal published the results of an experiment on insomnia. The experiment investigated the effects of a controversial new therapy for insomnia. Researchers measured the insomnia levels of 78 adult women who suffer moderate conditions of the disorder. After the therapy, the researchers again measured the women's insomnia levels. The differences between the the pre- and post-therapy insomnia levels were reported. Identify the experimental units.

A) the disorder ( insomnia or no insomnia)
B) the 78 adult women who suffer from insomnia
C) the differences between the pre- and post-therapy insomnia levels
D) the therapy time period (pre or post)