In Gallup's Study of Chimpanzee Behavior, How Did the Chimps

In Gallup's study of chimpanzee behavior, how did the chimps' behavior change from day 1 to day 3 when a mirror was placed in their line of sight?

A) On both days they showed no interest in the mirror at all.
B) From the start they treated the mirror much as a human would by occasionally grooming themselves.
C) At first they behaved as if they were looking at a different chimp (bobbing, threatening, etc.) , and then started to respond with self-directed responses such as grooming.
D) At first they behaved with self-directed behaviors such as grooming, but gradually started to behave as if a second chimp was present and became aggressive.