The answers are 1d, 2d, 3b, 4a and 5e.
1. All the alternatives state that roundbills colume cockaballs. Therefore this must be so - they can't all be false. Since not more than one answer is true it must be the minimal one, ie (d).
2. We see that (c) cannot be true because then (a) or (b) would also be true. Conversely, (a) cannot be true because then (c) would be true. Likewise for (b). So (d) is it.
3. The least inclusive answer must be the only true one. Since (a), (c) and (d) all say more than (b), it must be true.
4. Since 1(c) is false and 1(d) is true we know that roundbills don't colume albatrines. Since 2(a) is false we know that tar-eagles don't colume albatrines either (which may be quite a relief to any reader who happens to be an albatrine). So 4(a) is true. (Forget the rest!)
5. This one is a bit hairy. Since 4(a) is true we know that tar-eagles do not colume albatrines. Now 5(a) makes a statement about those tar-eagles that colume albatrines. Since there aren't any, this statement is not about anything and hence neither true nor false. See proof below.
One cannot say of zero horses that they are green, say. On the face of it a statement such as, "All the horses inside this matchbox are green," is not false, since it can only be false if there is a horse in the matchbox which is not green. Since the statement is not false it must be true.
This is a fallacy, as not all statements are either true or false. The canonical example is the self-referential statement, such as "This statement is false". In fact, the statement that every horse in the matchbox is green is neither true nor false, but simply meaningless. A statement without a referent is without meaning.
Otherwise, we could subtract one horse (h1) from the set having just one horse (h1) and observe that the remaining horses (ie none) have the colour of h1. We can also state that all the horses in the resulting (empty) set had any colour we cared to name, for instance the colour of whatever other horse we cared to think of eg h2. So the horse h2 would have the same colour as the non-existent horses in the empty set, which also have the same colour as the horse h1. Ergo h1 and h2 have the same colour. We can only avoid this paradox by not allowing the statement that a non-horse has a colour. In effect, non-existent things do not have properties and hence are not fit for discussion.
So statement 5(a) is neither true nor false.
5(b) is false since 1(b) is false and 1(d) is true.
5(c) is false because 4(a) is true.
Since 3(b) is true and 3(c) is false, we know that roundbills do not redell cockaballs. This makes 5(d) false.
Since a, b, c and d are not true, it follows that 5(e) must be true.