Assumption problem-Help

I saw this question on kaplan book, don’t know what is the different between chocie a and b. They seems to be contraceptive of each other.

Stimulus: Vague laws set vague limits on people’s freedom, which makes it impossible for them to know for certain whether their actions are legal. Thus, under vague laws people cannot feel secure.

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

A people can feel secure only if they know for certain whether their actions are legal.(Correct Answer)

B if people don’t know for certain whether their actions are legal, then they might not feel secure.


From the stimulus, I got

the evidence if Vague laws—not know if legal
the conclusion if vague laws —not feel secure

so the assumption is if not know if legal ---- not feel secure

both A and B choice come from this.

Can anyone help me with this? thanks

Stimulus says “cannot”…answer b uses “might not”. So answer b is wrong.

^^ Basically, vague laws → not knowing what’s legal → not feeling secure, period. B is more like not knowing what’s legal → POSSIBLY not feeling securing.

Thank you guys, I guess I need to be more careful on possibility word next time.