In order to prove that learning has happened, it is necessary to A. measure performance objectively and concretely
B. repeat each learning event at least three times
C. ask the subject if learning has actually occurred
D. determine whether the correct process was followed

Dominic and stacy each have a stamp collection. dominic has six fewer stamps than three times the number of stamps stacy has. dominic and stacy decide to give all of their stamps to their younger sister, mary. if stacy had s stamps, which expression represents the number of stamps that mary received? a. (3s − 18)(3s − 6) b. 2s − 18 c. 4s − 6 d. 4s − 18