Dear septwibowo,

I have many things to say in response, my friend.

First of all, I want to acknowledge TaN1213 for an intelligent and thoughtful response. I completely agree with TaN1213.

Next, septwibowo: you got a brilliant explanation from TaN1213 and, rather than learning the deep point that this user presented, you presented a counterargument. One of the deepest questions any student can ask himself is, "Do I want to be right or do I want to learn as much as I can?" You see, it's a paradox: of course on test day, you primarily want to be right (although you can learn even there), but the way to get to that is by disattaching from a need to be right while you are in the role of a student, because being holding to a position of being right can prevent you from picking up a new subtlety.

In this GMAT SC problem, choice (B) is precisely the kind of incorrect answer choice that acts as a trap for non-native speakers: it's 100% grammatically correct but wrong. Virtually all the high level SC questions have at least one such choice. This is a classic predictable trap and you fell into it.

Yes, the "is due to" construction in (B) is 100% grammatically correct. There's absolutely no ambiguity about that: you and I and TaN1213 are in full agreement about that. It's true and also completely besides the point. Choice (B) is 100% grammatically correct but it's still wrong. That's the piece you are missing: you are focused on the grammar and missed that TaN1213's brilliant response was addressing other aspects of the sentence beyond the grammar.

The GMAT SC is NOT primarily a test of grammar. On the GMAT SC, grammar & logic & rhetoric all combine to support meaning.

The principles of good rhetorical construction can be hard for non-native speakers to appreciate, because much of it is intuitive--it's about the "feel" of the sentence. Here's one principle that I can articulate: when a sentence is focused on a main action, this sentence usually will be phrased in the most direct and powerful way when that main action is the main verb of the sentence.

Choice (A) follows this principle fully. Choice (A) is not only grammatically correct but also direct, clear, and powerful. Like almost all correct answers on the GMAT SC, it's an exceptionally well-crafted sentence.

Choice (B) is 100% grammatically correct but it's an embarrassingly awkward and punchless sentence. In particular, the main action of the sentence, "tripling," is congealed as a gerund subject, and the sentence is organized so that a complete non-action verb, "is," winds up as the main verb of the sentence. Any well-read native speaker instantly would recognize this as a poorly written section. The fact that you selected choice (B) as correct and were willing to defend it should tell you a great deal about the progress you still have to make.

Grammar has a lot of rules, although many of the rules have exceptions. Rhetoric doesn't have many rules--it's more intuition-based. A non-native speaker can develop this intuition by cultivating a rigorous habit of reading. See:
How to Improve Your GMAT Verbal Score

Does all this make sense?
Mike

Consider the following examples:

• The game was postponed due to rain.
• Dave is cool.
• Dave's success was due to his hard work.

In the first example, "due to" modifies the verb "was postponed" (Why was the game postponed? Due to rain). But using "due to" to modify a verb seems to be a no-no on the GMAT.

In the second example, we have a linking verb ("is"), and "cool" modifies "Dave". (A fellow named Dave may or may not have played a role in writing these sentences. )

In the third example, we have another linking verb ("was"), and "due to" actually modifies "success". "Due to" can modify a noun, so this is okay.

Similarly, in choice (B), "due to" actually modifies "a tripling", which is a noun. So the usage of "due to" in choice (B) is totally fine.

I hope this helps!