```
class A:
    B = range(10)
    C = frozenset([4, 5, 6])
    D = list(i for i in B)
    E = list(i for i in B if i in C)
```

```

coreyf@frewbook-pro /tmp [1]> python3 a.py
Traceback (most recent call last):
  File "a.py", line 1, in <module>
    class A:
  File "a.py", line 5, in A
    E = list(i for i in B if i in C)
  File "a.py", line 5, in <genexpr>
    E = list(i for i in B if i in C)
NameError: name 'C' is not defined
```

Why should I be able to access B but not C?