Final answer:
The subject of the sentence 'Some mushrooms are poisonous' is 'Some mushrooms'
Step-by-step explanation:
In the given sentence, the subject is 'Some mushrooms'. The subject of a sentence is the noun or pronoun that performs the action or is being described in the sentence. In this case, 'Some mushrooms' is the subject because it is the noun being referred to.
Learn more about subject of a sentence