Answer to Question 1
The ABAB is a single-subject design which consists of a period of no treatment (A) or baseline, during which the behavior of interest is repeatedly measured. After a stable picture of behavior has been established, the treatment (B) is begun. Behavior is monitored throughout the treatment phase until it appears the treatment is having an effect and the behavior stabilizes. This is followed by a second A phase, in which the treatment is withdrawn or reversed. Again, behavior is monitored to observe the effect. For ethical reasons and the replication benefit, a treatment phase(B) is again instituted.
Answer to Question 2
E