Question

in a study in which infants were shown videos of a stranger either comforting or ignoring a crying infant, even 4 - month - old - infants were more surprised by the video in which the stranger ignored the infant. this behavior shows that
infants reactions are due solely to their genetic code.
infants reactions to other infants are more pronounced.
infants only look at adults they might recognize.
infants have expectations about how other people will behave.

Explanation:

The study shows that infants react differently (more surprise) to a behavior (ignoring) that goes against an expected norm (comforting). This indicates they have some expectation of how people (the stranger) should behave. Genetic code (first option) is too absolute as environment also plays a role. The second option about reactions to other infants is not the focus (the focus is on stranger - infant interaction). The third option about recognizing adults is not relevant to the behavior of expecting comforting.

Answer:

infants have expectations about how other people will behave.