Step 1: Analyze the passage.
The passage argues that resisting temptation is the only way to understand its strength. People who give in easily never truly understand the struggle, and thus do not really know badness or goodness.
Step 2: Evaluate the options.
- Option A: This aligns perfectly — only through testing (resisting temptation) do we truly know the strength of our beliefs or character.
- Option B: Too broad and vague. The focus here is specifically on resisting temptation, not on all knowledge.
- Option C: Exaggerated. The passage does not claim about “most of the population,” just about people who give in.
- Option D: Partially true, but narrower. The conclusion is about testing beliefs, not just “knowing temptation.”
- Option E: Interesting, but not as precise. The key point is testing beliefs, not labeling ourselves.
Step 3: Best conclusion.
Option A most accurately captures the essence of the passage.
Final Answer:
\[
\boxed{\text{A}}
\]