= Solution
The five printed lines, including the comma and space after every fragment, are:
``
f1 in C,
f1 in C, f2 in B,
f1 in C, f2 in A, f3 in B,
f1 in A, f2 in A, f3 in ObjB, f4 in B,
f1 in ObjC, f2 in A, f3 in B, f4 in ObjC, f5 in C,
``
<Scala> <dynamic dispatch> uses the receiver's runtime <software class>, even though `a` has the <static type> `A`. Thus `a.f1` uses `C.f1`, and `a.f2` uses `B.f2` whose unqualified `f1` still dispatches on the `new C` receiver.
For `a.f3`, `B.f3` explicitly selects `super.f2`, which is `A.f2`. Inside `A.f2`, the unqualified call to `f1` still dispatches to `C.f1`; `super` does not replace the receiver. For `a.f4`, `B.f3` in the body of class `B` means a call on the <singleton object> `B`, not on `this`. That object's `f3` calls `A.f2`, which calls `A.f1`.
Finally `a.f5` calls `C.f4` on the <singleton object> `C`. That object extends class `B`, overrides `f1` and `f4`, and inherits class `B`'s `f3`. Its `f4` calls this inherited `f3`; that selects `A.f2`, whose `f1` dispatches to the object's own override. These distinctions follow member selection and `super` semantics.<Scala 2.11 expressions specification>[This and Super; Designators, member selection]{ref}
$$
\boxed{\text{Ordinary calls keep the receiver; explicit B and C name their singleton objects}.}
$$
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