The simple subject is "demonstration."
demonstration You can tell more easily by rewriting the sentence in standard word order: A spontaneous demonstration rumbled from somewhere in the middle of the crowd.
demonstration
demonstration
The subject would be "demonstration."
Simple Subject: demonstration
[A spontaneous demonstration] rumbled from somewhere in the middle of the crowd.Note: In this sentence the noun "demonstration" is the simple subject. This is arrived at by asking the verb rumbled a "what" question. Here though the words "a" and "spontaneous" do modify the simple subject and are properly treated as a part of the full subject in general.
[A spontaneous demonstration] rumbled from somewhere in the middle of the crowd.Note: In this sentence the noun "demonstration" is the simple subject. This is arrived at by asking the verb rumbled a "what" question. Here though the words "a" and "spontaneous" do modify the simple subject and are properly treated as a part of the full subject in general.
[A spontaneous demonstration] rumbled from somewhere in the middle of the crowd.Note: In this sentence the noun "demonstration" is the simple subject. This is arrived at by asking the verb rumbled a "what" question. Here though the words "a" and "spontaneous" do modify the simple subject and are properly treated as a part of the full subject in general.
'Spontaneous' means "arising from a momentary impulse". There is no animal which represents 'spontaneous'.
This sentence doesn't have s+v+O word order so it is not easy to pick the s+v. If you rewrite the sentence:A spontaneous demonstration rumbled from somewhere in the middle of the crowd.The verb is rumbled, so ask your self - what rumbled? - and the answer is "A spontaneous demonstration". If the subject is a noun phrase then the simple subject is just the noun. In this case the noun is demonstration.Probably the word order of the sentence is changed for effect.
The first animal to die on the farm (while it's still known as "Manor Farm") is Old Major. The first animal to die after the farm was renamed "Animal Farm" is a sheep in the Battle of the Cowshed.