Consider the following class definitions:

`class A: def init(self, attr1): self.attr1 = attr1

class B(A): def init(self, attr1, attr2): super().init(attr1) self.attr2 = attr2

class C(A): def init(self, attr1, attr3): super().init(attr1) self.attr3 = attr3

class D(B): def init(self, attr1, attr2, attr4): super().init(attr1, attr2) self.attr4 = attr4`

If you create an instance d = D(1, 2, 4), what attributes does d have access to?