Question: Both y and z are immutable references pointing to fixed-size collections of the same four integers. Are there any differences?

1. You can modify the contents of the elements in `y` but not `z`.
2. There are not any differences. `y` and `z` are a type alias of the same type.
3. You add more elements to `z` since it is a list.
4. You can modify the contents of the elements in `z` but not `y`.

Answer: The correct answer of the above question is Option A:You can modify the contents of the elements in `y` but not `z`.