Answer:
The correct option here is D) mutable
Step-by-step explanation:
When there is a change in the value of a object or identity over a period of time , it is called as mutable, and when the value of an object or identity doesn't change over time , it is called as immutable.
In this case Barbara's son , Steven has not made any change in its identity, but Barbara expected that his identity should have changed as he grew up , so we can say that she was expecting the concept that identities are mutable.