This is one of those questions where people are just posting their votes for all the options...A,B,C,D,E.

I think there is no best answer among either of the options. What we can find is the one better answer than other four options.

So we need to understand which one is the more severe problem among
Error# 1 : "Wrong modifier", (A, B, C)
Error# 2 : "Passive Voice sentences", (D, E)
Error# 3 : "Use of 'As If' in the sentence" (D)
Error# 4 : "Possibility of 'they' referring either to travellers or inspectors" (D) or
Error# 5 : "Lack of Parallelism between 'Not like' and 'but'" (E)

Now I think, Error# 1 is the most severe, so should also be avoided.
Error# 5 is second most severe error, so should be avoided over others.

And that's why I also think 'D' as the better answer than others.
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http://gmatclub.com/forum/a-guide-to-the-official-guide-13-for-gmat-review-134210.html
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Its A ,when two nouns are compared Like should be used
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+1 Kudos If found helpful..

The correct answer is D.

A - C are out as the sentences all incorrectly modify travelers instead of customs inspectors. With choice D, there is some confusion as to what "they" modifies. I'm going to copy Ron Purewal's response from Manhattan GMAT as to why "they" can be used and why ambiguous pronouns should be one of the last rules you use to invalidate a sentence.


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quote: Ron Purewal

from a purely technical standpoint one could regard this pronoun as ambiguous, but remember that many technically ambiguous pronouns are actually acceptable on the gmat.

for the precise conditions under which ambiguous pronouns are most commonly acceptable, see the following two posts:

----- READ THESE POSTS FIRST -----

post30203.html#p30203
post35036.html#p35036


----- ONCE YOU'VE READ THOSE POSTS -----

note that these conditions also apply in the current sentence.

1) clear context: if you understand what the sentence is trying to say, it's clear that "they" is intended to stand for customs inspectors, not travelers.

2) parallelism/nonparallelism:
"they" is the SUBJECT of its clause
"customs inspectors" is the SUBJECT of its clause
"travelers" is not the subject of its clause (it's the object of a preposition)

since both sets of conditions are satisfied, this is an example of a technically ambiguous pronoun that is still perfectly acceptable.

'No matter how patiently they explain their reasons for confiscating certain items', this modifier should modify customs officer, so D and E left.

D is the best option.

But if travelers is near treated that will mean travelers are treated and that will change meaning of sentence. Choice D also appears to be passive (To be+ past participle indicated by 'by' in the end)