The meaning of "expired" as it is used in this sentence is: past the date of being safe to drink.
The meaning of "expired" as used in this sentence is "past the date of being safe to drink." To arrive at this answer, we can analyze the sentence and the context. Benjamin's reaction of making an awful face and exclaiming that the milk is expired suggests that it has gone bad and is no longer fit for consumption. Therefore, the correct choice is "past the date of being safe to drink."
