Answer:
The complete subject of the sentence "Mrs. Marcus told our class about Valentine’s day" is the "valentine’s day".
Explanation:
This is because the sentence talks about the complete subject of valentine’s day and the class is informed about the details of the "valentine’s day" by Mrs. Marcus. This is the simple subject which is being talked about in the class so that the students get complete idea of the topic. Thus, the simple and the complete subject here is valentine’s day.
