Q1 - Walter: Although cigarette smoking

[alex.cheng.2012]

I got the question correct (the correct answer is A), and although I knew A was the better answer, I had trouble eliminating B (A was so perfect I almost wanted to just pick it and move on, but knowing this was for review, I went ahead and read the rest of the answers finding reasons to eliminate them all)

(B) states that an activity should be banned if in most situations that activity would inevitably expose someone to harm (not exact words, but it's pretty much what the answer says)

Couldn't this also fill the role of justifying Walter's conclusion?

An activity, the activity of smoking cigarettes on a plane, should be banned if in most situations (and as the premise shows, it's actually in ALL situations, which would include most) it would inevitably expose someone to harm (as the argument says, the harm is unavoidable, so it's not a stretch to say such harm would inevitably be exposed to someone).

Can someone help me understand the correct reason to eliminate B? Thanks in advance.

[ohthatpatrick]

No problem ... you were just reading (B) as "if", not "only if".

Those are diagrammed two opposite ways.

For example, these are two equivalent sentences:
If you have a driver's license, then you passed the written test.
You have a driver's license only if you passed the written test.

If it said "if", we'd get:
Most times ppl engage in this activity it harms others --> ban it

Since it says "only if" we get:
Ban it --> most times ppl engage in this activity it harms others

Just like Sufficient Assumption, Principle-Justify answers are almost always conditional ideas, so sometimes it's not enough to just locate the right ideas; we need to also verify that they're presented in the correct logical order.

Since the conclusion is "it should be banned", we need a rule that works like
if [something from the premise] ---> then should be banned

Hope this helps.