Dear Harley1980,
I'm happy to respond. As usual, it warms the cockles of my heart to see a question I wrote posted here on GC.

So, this is an interesting one. The homeowner person first states the fact, the evidence that burglars target houses that appear unoccupied. Then, the homeowner person suggests a plan of action, leaving the lights on, which this person thinks will convince burglars that the house in unoccupied.

The crime expert doesn't introduce any new evidence, because evidence is an objective fact to which everyone would agree. He gives his interpretation of how a burglar would respond to a house with lights continuous on, and in his interpretation, there is an undesirable effect of this action.

There's no unstated assumption pointed out, so (A) is not right at all.
There's no confusion of cause & effect, so (D) is not right at all.
The two people don't agree, so (E) is not right at all.

The tricky trap answer is (C). You see, what the Crime Expert says does not count as "evidence" in GMAT terms. Evidence is something we all could read in the newspaper or look up in a reference book, an objective fact on which there is general agreement. Now, what the Crime Expert said could be objective true. Maybe if we went out and surveyed thousands of burglars ("Excuse me, sir, are you a burglar? I have a few survey questions to as you."), then we could gather objective evidence and call this position a fact. There is no attempt, in the course of the prompt argument, to advance such claims. The crime expert is giving us his opinion. Now, this is an opinion informed by his years of experience in the field, so it much more valuable and weighty than the opinion of a non-expert. Nevertheless, it fails short of the high mark that the GMAT holds for "evidence."

This leaves the OA, (B), which hits the nail on the head.

Does all this make sense?
Mike
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Official Explanation

The homeowner representative recommends leaving the lights of an empty house on as way to prevent crime. The crime expert points out that leaving the lights on like this will invite crime.

The credited answer is (B). Giving potential criminal information about who is on vacation would be an unintended and undesirable effect of the homeowner representative's recommendation.

The homeowner representative explicitly states that he thinks keeping lights on will make would-be burglars assume someone is home, so that's not a "unstated" assumption. This is why (A) is incorrect.

What the crime expert is pointing out may be an interpretation or an argument, but it's not really evidence. Evidence would be some unambiguously agreed upon fact. This is why (C) is incorrect.

In this question, leaving the lights on causes various interpretations; clearly, the interpretations of would-be burglars don't cause the lights to go on. This is why (D) is incorrect.

The crime expert does not agree that the homeowner representative's conclusion is true. This is why (E) is incorrect.
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Home owner representative recommendation : leave lights on to avoid possible vulgary

Crime expert : leave lights on can also give impression that the house is unoccupied if undisturbed for prolonged time

A- leaving lights on would give an impression that the house is occupied and will ward off potential vulgary is a stated assumption.
B- leaving light on to avoid potential vulgary may work if burglar thinks the house is occupied, but it may not work if burglar thinks the house is not occupied because the light has been on undisturbed

Crime expert talks about the potential drawbacks of the recommendation
B is correct

I hope my explanation helps!
Posted from my mobile device

A) calling into question an unstated assumption - the crime expert attacks what is explicitly stated
B) pointing out an undesired effect of a recommendation - CORRECT : desired effect is a burglar getting a clear signal.
C) presenting new evidence that calls the conclusion into question - no new evidence
D) explaining that a reputed effect is actually a cause - burglary is not a cause
E) demonstrating that the conclusion is true, but not for the reasons cited- irrelevant