Answer:
Option (a).
Explanation:
Ebbinghaus Forgetting Curve may be defined as the curve that are used to determine the decreases ability of the brain to memorize the thing. This was first hypothesized by Ebbinghaus.
The ability of memorize the things will depend upon the individual and on the strength of the memory. As Raven was 100% recall the the end of class, she can forget the 40% memory by leaving at the rest 20 minutes after the class. The memory retain with her long that gas the high strength.
Thus, the correct answer is option (a).