Hello Everyone!
Let's tackle this question, one issue at a time, to find the correct choice! Before we dive in, here is the original question with any major differences between the options highlighted in orange:
According to scientists who monitored its path, an expanding cloud of energized particles ejected from the Sun recently triggered a large storm in the magnetic field that surrounds Earth, which brightened the Northern Lights and also possibly knocking out a communications satellite.
(A) an expanding cloud of energized particles ejected from the Sun recently triggered a large storm in the magnetic field that surrounds Earth, which brightened the Northern Lights and also possibly knocking
(B) an expanding cloud of energized particles ejected from the Sun was what recently triggered a large storm in the magnetic field that surrounds Earth, and it brightened the Northern Lights and also possibly knocked
(C) an expanding cloud of energized particles ejected from the Sun recently triggered a large storm in the magnetic field that surrounds Earth, brightening the Northern Lights and possibly knocking
(D) a large storm in the magnetic field that surrounds Earth, recently triggered by an expanding cloud of energized particles, brightened the Northern Lights and it possibly knocked
(E) a large storm in the magnetic field surrounding Earth was recently triggered by , brightening the Northern Lights and it possibly knocked
After a quick glance over the options, there are 2 main things we can focus on:
1. Modifiers (Are the scientists monitoring the cloud or the storm?)
2. Parallelism (brightened/brightening & knocked/knocking)
Let's start with #1 on our list: modifiers! We have to ask ourselves a couple questions to determine what order the modifiers should be in:
WHAT were the scientists monitoring?
and
WHAT brightened the Northern Lights and possibly knocked out a communications satellite?
We can tell by reading the sentence carefully that the scientists were monitoring THE CLOUD. This means the modifier "According to scientists who monitored its path" needs to come directly before the storm, which is what it's referring to! Let's see which options handle this correctly, and rule out those that don't:
(A) an expanding cloud of energized particles ejected from the Sun recently triggered a large storm in the magnetic field that surrounds Earth, which brightened the Northern Lights and also possibly knocking
(B) an expanding cloud of energized particles ejected from the Sun was what recently triggered a large storm in the magnetic field that surrounds Earth, and it brightened the Northern Lights and also possibly knocked
(C) an expanding cloud of energized particles ejected from the Sun recently triggered a large storm in the magnetic field that surrounds Earth, brightening the Northern Lights and possibly knocking
(D) a large storm in the magnetic field that surrounds Earth, recently triggered by an expanding cloud of energized particles, brightened the Northern Lights and it possibly knocked
(E) a large storm in the magnetic field surrounding Earth was recently triggered by an expanding cloud of energized particles, brightening the Northern Lights and it possibly knocked
We can rule out options D & E because they don't put the modifier next to what it's modifying.
Now that we're left with only 3 options, let's move on to #2 on our list: parallelism. There are two things that happened as a result of the large storm in Earth's magnetic field: the Northern Lights were brighter, and it possibly knocked out a communications satellite. These two need to be written using parallel structure! Let's see which ones do, and rule out those that don't:
(A) an expanding cloud of energized particles ejected from the Sun recently triggered a large storm in the magnetic field that surrounds Earth, which brightened the Northern Lights and also possibly knocking --> NOT PARALLEL
(B) an expanding cloud of energized particles ejected from the Sun was what recently triggered a large storm in the magnetic field that surrounds Earth, and it brightened the Northern Lights and also possibly knocked --> NOT PARALLEL
(C) an expanding cloud of energized particles ejected from the Sun recently triggered a large storm in the magnetic field that surrounds Earth, brightening the Northern Lights and possibly knocking --> PARALLEL
There you go - option C is the correct choice! It places the modifier next to what it's modifying, and it uses parallel structure for both effects at the end!
Don't study for the GMAT. Train for it.