To my dear instructors, Stacey and Ron, I am having an issue understanding the usage of the term "extending". I have come across three similar questions that test this concept, and my comprehension is still lacking.
One example comes from the OG, so I will not be posting it. The other two examples come from the Quest for 750: Sentence Correction Slam Homework Bank.
Question 8:
Vietnamese researchers have recently conducted the first comprehensive study of what could be the most expansive architectural structure found in northern Vietnam, a labyrinth of narrow tunnels constructed around 400 B.C. and extends for more than 25 miles underground.
The explanation of why "extends" should be "extending" from MGMAT is as follows: This answer choice supplies the appropriate modifier "extending" that is idiomatic and structurally parallel to the previously mentioned modifier "constructed." Both modifiers refer to the "labyrinth of narrow tunnels" and thus must be structurally and logically consistent. (Note: To my surprise, the OG guide's explanation does a slightly better job at explaining this, but again, I cannot post it, and even if I could, it still goes over my head).
1. First, how is "extending" parallel to "constructed"?
Wouldn't it be "extended" that is parallel to "constructed"?
Why would "extended" be incorrect in this context?
2. Second, this clause makes sense to me:
...a labyrinth of narrow tunnels constructed around 400 B.C.
However, this clause sounds completely awkward:
...a labyrinth of narrow tunnels extending for more than 25 miles underground.
Wouldn't it have to be
...a labyrinth of narrow tunnels [that is] extending for more than 25 miles underground.
or
...a labyrinth of narrow [tunnels'] extending for more than 25 miles underground.
Question 29:
Egyptian geologists have recently discovered what could be the largest pre-historic irrigation system found to date, a sophisticated structure of interwoven pipes created more than 5,000 years ago and extending for more than 12 miles from the Nile delta.
The issue with "extending" and "created" here is analogous to "extending" and "constructed" above.
I would love a detailed explanation about this term "extending". Thanks!