Apark ranger records the daily number of individuals who visited a park for six months before and six months after an admission fee was implemented. during the same time period, he compares the number of visits to two comparable parks that have no admission fee. this quasi-experimental design would be an example of a(n)

(a) nonequivalent control group pretest-posttest design.
(b) interrupted time series design.
(c) control series design.
(d) reversal design.