I need some help on this question; most of the answers appear the same to me. Could someone please explain why the credited answer is the only correct one?

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

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

Correct answer (E) Knowing a proposition to be true requires proving it true by obervation.

My incorrect answer selected (C) If a proposition can be proven true by observation, then it can be known to be true.

Extra points for someone who can explain what is wrong with the answer I selected.

Thanks.

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

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

Correct answer (E) Knowing a proposition to be true requires proving it true by obervation.

My incorrect answer selected (C) If a proposition can be proven true by observation, then it can be known to be true.

Extra points for someone who can explain what is wrong with the answer I selected.

Thanks.