Bunuel
Alongside Petra and the Great Wall of China as one of the seven wonders of the modern world, the Taj Mahal, which was constructed to memorialize Mumtaz Mahal, the third wife of emperor Shah Jahan, after her passing took more than 12 years of thousands of engineers' labor to build.
A. the Taj Mahal, which was constructed to memorialize Mumtaz Mahal, the third wife of emperor Shah Jahan, after her passing took more than 12 years of thousands of engineers' labor to build
B. Mumtaz Mahal, the third wife of emperor Shah Jahan, was memorialized after her passing by the Taj Mahal, which thousands of engineers who labored more than 12 years to build it
C. it took thousands of engineers more than 12 years to build the Taj Mahal to memorialize Mumtaz Mahal, the third wife of emperor Shah Jahan, after her passing
D. thousands of engineers labored more than 12 years to build the Taj Mahal to memorialize Mumtaz Mahal, the third wife of emperor Shah Jahan, after her passing
E. more than 12 years were needed to build the Taj Mahal, which thousands of engineers labored at to memorialize Mumtaz Mahal, the third wife of emperor Shah Jahan, after her passing
Official Explanation
Creating a filter: the original sentence is a bit confusing. The phrase "after her passing," in particular, is not optimal. The sentence makes it sound like it took more than 12 years to build after her passing, but maybe additional time before her passing, which is probably not the intended meaning of the sentence.
Applying the filter: the answer choices are diverse. They all begin differently. In fact, the beginning of the answer choice comes directly after the modifying phrase that begins with "Alongside Petra..." Nothing other than the Taj Mahal can fit into that slot and be compared with Petra and the Great Wall of China. Answer choice (A) is the only viable option, despite its flaws, because it's the only one without a gross modifier error.
The correct answer is (A).