"The cat was scared from the sound." << regional or vernacular version of "by the sound" "The cat was scared by the sound." << standard "cat" [grammatical subject] "sound" [agent] More information: "by the sound of things" [= I have heard news] "from the sound of things" [= I have heard news] https://www.ldoceonline.com/dictionary/by-from-the-sound-of-it-things "The cat was afraid of dogs." "The cat was scared of dogs." [general condition] "The cat was scared by the black dog." [completed action - simple past - passive voice]

Sound would be the subject, although "from" doesn't seem right - normally "by".

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