A compound subject for impact would have to be two words that are subjects in the beginning of the sentence and the word impact would have to be in the sentence somewhere.
Greenhouse gases have had a significant impact on the environment.
Brace for impact - we'regoing in!Please hand me that impact wrench.
The impact of the closing that factory will be huge on the local economy.
"You're making a big impact in my life!" screamed Tiffany.
Removing the word "very" would have no impact on the meaning of the sentence
We are bracing ourselves for the worst.Or, begin the bracing for impact!
The impact on local amenity can also be greater in small settlements.
The impact of the meteor created a crater in the earth.The community has been badly impacted by sustained poverty.
Martin Luther King Jr's impact on the world was benieficial.
Yes correct.
The hard impact with the floor caused the vase to shatter.