Since the modifier "a Malaysian state..." is not underlined, we can ignore it entirely. Focus on: "Recently observed tourism trends in Sabah include...." Following the word "include," there are two trends. Even when a list has only two items, those items must be grammatically parallel. In the sentence as written, "interest increasing" and "numbers growing" are parallel, but not correct. "The interest increasing in travelers..." sounds more like people have interest in those travelers than the travelers having an interest in something. The latter is what makes logical sense.

The other choices have similar problems. While they are grammatically parallel, many of them don't make sense. In choice (B), "travelers whose interest increased" sounds like specific travelers developed an increased interest in national parks. (C) is similar though with a different grammatical construction: "travelers interests that increase" doesn't have the intended meaning of "more interest from travelers" in general.

Choice (D) has a similar issue as the original sentence. "The interest increase" doesn't clearly refer to travelers having more interest; it could just as easily refer to someone else having more interest in travelers. That leaves on (E), which is correct. "Increased interest from travelers" makes it clear that the travelers have an interest in the parks, and that the "interest" has increased from travelers in general, not from a specific traveler.