Hi carcass
Please provide an explanation for this one. This one has me confused a lot. There are a lot of things different in the answer from the original sentence.
I feel the answer option deviates from the original a lot.

1. Maintenance and Maintaining- Maintenance is actions performed to keep machinery or system in check and maintaining is the act of doing maintenance. Though both nouns, there's a difference.

2. employment-to-population ratio balance and the balanced employment-to-population ratio- The former to me seems to suggest that the ratio can vary as in the employment can increase or population can increase but we decrease or increase population or employment respectively to maintain a balance. The latter "balanced employment-to-population ratio" seems different as in not only it's fixed but there are some other factors that are contributing to the ratio to make it balanced. For example, a balanced diet might mean a mixture of vegetables, fruits, and meat to provide all the nutrients, minerals, and vitamins and not mean a balance between ratios of carbs, proteins, and fats. This could just be my misunderstanding as well.

3."employment-to-population ratio balance, after being affected by economic factors" and "threat, after economic factors, to native citizen......." - Now, I took the first sentence to mean that we are trying to maintain employment-to-population ratio balance after it has been affected by economic factors arisen due to automation. But the other options just change the meaning to mean automation is the most serious threat after economic factors, meaning economic factors are the more serious threat than automation. Economic factors essentially mean factors that can affect an individual's financial status but we don't know whether positively or negatively. So, to me just saying Economic factors are a threat seems a bit odd but I can be mistaken as well.

I chose A because others seemed a little too off from the meaning or maybe I misinterpreted the intended meaning. I'll leave it to you carcass to help clear my doubts. Thanks as always.

A. threat to native citizens of the US as well as to maintaining employment-to-population ratio balance, after being affected by economic factors.
"after being affected" seems to intend the meaning that automation is affected.
"to maintaining" is not parallel "to natives"

B. threat, after economic factors, to native citizens of the US and for maintaining a balanced employment-to-population ratio.

"to native citizens" and "for maintaining", not parallel. distorts meaning.

C. threat, after factors affecting its economy, to native citizens of the US and also to the maintenance of a balanced employment-to-population ratio.
"it's economy"?? incorrect
"and also" redundant


D. threat to native citizens of the US and for maintaining balanced employment-to-population ratio, after economic factors.

same error as B

E. threat, after economic factors, to native citizens of the US and to the maintenance of balanced employment-to-population ratio.

CORRECT. parallelism is established.

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Option A: Parallelism Error. “Threat to native citizens.. and to maintaining”.
Option B: Parallelism Error. “Threat to native citizens.. and for maintaining”.
Option C: Parallelism is not maintained due to the phrase “and also”. Moreover, the phrase “and also” is redundant.
Option D: Parallelism Error. “Threat to native citizens.. and for maintaining”.
Option E: The parallelism is maintained, and there are no pronoun errors.

Answer: E
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