The Study Examining Infants' Ability to Do Simple Arithmetic That

The study examining infants' ability to do simple arithmetic that showed infants one or two dolls and then either added or subtracted a doll from behind a screen demonstrated that infants were surprised when which of the following events occurred?
•A doll is placed behind a screen where another doll was initially present, and lowering of the screen reveals a single doll.

A) A doll is removed from behind a screen where two dolls were initially present, and lowering of the screen reveals a single doll.
B) A doll is placed behind a screen where another doll was initially present, and lowering of the screen reveals two dolls.
C) A doll is removed from behind a screen where two dolls were initially present, and lowering of the screen reveals two dolls.
D) Both A and D are correct.
E) Both B and C are correct.