Final answer:
The correct answer is option a. The subject of the sentence 'When are the parades this summer?' is 'parades', making option a the correct answer. 'When' is an interrogative pronoun asking for the time, while 'parades' is the main noun (simple subject) being inquired about.
Step-by-step explanation:
The subject of the sentence 'When are the parades this summer?' is the noun or noun phrase that the sentence is about. In this case, it's asking about a particular time or occasion when events are taking place. The word 'when' is serving as an interrogative pronoun, aimed to question the time of an event. The word 'parades' is the main noun which is being queried about. It is the simple subject because it is the focus of the question.
Option 'a' for 'parades' is the correct response because when we look for the subject of a sentence, particularly a question, we identify the noun that is being questioned or described. 'Summer' and 'this' give us more information about the noun, but they are not the subject themselves. Therefore, the subject in the sentence is option a, 'parades'.