Answer:
c. reticular formation
Step-by-step explanation:
Some of the functions of the reticular complex are cardiovascular control, somatic motor control, which includes breathing and swallowing, as well as some of the eye and ear function. It is also involved in pain modulation, sleep and alertness regulation (a serious damage could result in a comatose state), regulation of the attention, among other functions. Given the signs listed in the question (her breathing rate decreased dramatically, her heart slowed down, and her blood pressure decreased.), it indicates that the structure the drug is acting on, is the reticular complex. Also, being sleeping pills, it is very likely that they are targeted to there.