New theories propose that catastrophic impacts of asteroids and comets

Here you go: Check MGMAT SC chapter 10 or 11 if you have it

Concrete nouns vs action nouns vs complex and simple gerunds :

1/Concrete nouns: Refer to things, people, places dates… Ie: rock, continent, politician, holiday, week ...

2/Action nouns: Refers to action, they are formed from verbs Eruption, pollution, change, growth development etc

3/Simple Gerund: Include “ing”, presented as if they follow a verb
- ex: Tracking Satellites accurately is important
- Could be transformed into a working verb: I AM tracking satellites…

Complex Gerund: Starts by (a, an, the) or adjective, followed by ing + “of” prepositional
- ex: The accurate tracking of satellites is important…
- Of note: can also be under the form: the accurate satellites tracking – prefer the “of” version though

Parallel rules:

1.Concrete nouns are ONLY parallel to concrete nouns!
Wrong The bouquet was a giving of love
Correct The bouquet was a gift of love
- A giving is a complex gerund

2. Simple gerund are NEVER PARALLEL with complex gerunds
Wrong: I enjoyed drinking the water and the wine tasting
Correct I enjoyed drinking the water and tasting the wine
-drinking the water = simple gerund, the wine tasting = complex gerund

3. ONLY complex gerunds CAN PARALLEL with action nouns but when a proper action noun exists prefer it over a complex gerund
Wrong: The rebels demanded the withdrawal of the government forces from disputed regions, significant reductions in overall troop levels, raising the rebel flag on holidays, AND a general pardon
Correct: The rebels demanded the withdrawal of the government forces from disputed regions, significant reductions in overall troop levels, the raising of the rebel flag on holidays, AND a general pardon

Prefer an action noun over Gerund:
Wrong: The rebels demanded the withdrawal of the government forces from disputed regions AND releasing certain political prisoners (Simple Gerund used)
Wrong: The rebels demanded the withdrawal of the government forces from disputed regions AND THE releasing OF certain political prisoners (Complex Gerund used)
Correct: The rebels demanded the withdrawal of the government forces from disputed regions AND THE release OF certain political prisoners (action noun correctly used)