Final answer:
The subject of the sentence is 'puppy', which is a common noun.
Step-by-step explanation:
The subject of this question is English.
The sentence provided is: The puppy quickly jumped over the fence into the neighbors yard.
The subject of the sentence is 'puppy', as it is the noun that the sentence is primarily about. It is a common noun, which refers to a general type of dog, and is also the subject of the sentence.
Learn more about Parts of speech in a sentence