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Which preposition would you use in this sentence please?

1 There was an impending disaster on/in/for the city.
2 There was a looming disaster on/in/for the city.

How would you say the above?

AT or BY

1 She was crushed at/by the thought of her daughter dying/ about to die.

Thank you
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Another popular usage is "The city faced impending disaster." ". . . a looming disaster."

None of your preposition choices sound natural to me.

In your second example, I like "by." "Crushed" works better here as an action word (passive voice) than as an adjective ("to be" plus adj.)

"Devastated," on the other hand, works better as an adjective. (Devastated at)

My point is, "by" implies an action. "At" implies a quality.

We often say "a devastated person," but seldom "a crushed person."

"He was crushed by a log."
Comments  
As written, I would use for. However, I wouldn't normally write the sentences that way. I would say: "Disaster was looming for the city. (Or "over the city.")

In the other example, I would say it thus:
She was crushed by the thought of her daughter dying.
Or: She was crushed by the thought of her daughter being about to die.
Or, better: She was crushed by the thought of her daughter's impending death.
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 Avangi's reply was promoted to an answer.
Thank you.

So are IMPENDING AND LOOMING interchangeable?

Can you say it this way?

There was an impending/looming disaster over the city.
Disaster was impending/looming over the city.

Thank you
I suppose it's possible; but in these particular sentences, the natural way would be to use impending as the adjective (1st sentence), and looming as the verb (2nd sentence).
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