24. No mathematical proposition can be proven true by observation. It follows that it is impossible to know any mathematical proposition to be true

The conclusion follows logically if which one of the following is assumed?

(A) Only propositions that can be proven true can be known to be true
(B) Observation alone cannot be used to prove the truth of any proposition
(C) If a proposition can be proven true by observation then it can be known to be true.
(D) Knowing a proposition to be true is impossible only if it cannot be prove true by observation
(E) Knowing a proposition to be true requires proving it true by observation

25. The publisher of a best-selling self-help book had, in some promotional material, claimed that it showed readers how to become exceptionally successful. Of course everyone knows that no book can deliver to the many what by definition, must remain limited to the few exceptional success. Thus although it is clear that the publisher knowingly made a false claim. doing so should not be considered unethical in this case

Which one of the following principles if valid most strongly supports the reasoning above?

(A) Knowingly making a false claim is unethical only if it is reasonable for people to accept the claim as true
(B) Knowingly making a false claim is unethical if those making it derive a gain at the expense of those acting as if the claim were true.
(C) Knowingly making a false claim is unethical in only those cases in which those who accept the claim as true suffer a hardship greater than the gain they were anticipating
(D) Knowingly making a false claim is unethical only if there is a possibility that someone will act as if the claim might be true
(E) Knowingly making a false claim is unethical in at least those cases in which for someone else to discover that the claim is false that person must have acted as if the claim were true