Answer:
The correct answer is "The organizers of the event".
Step-by-step explanation:
The subject is that part of the sentence that agrees in person and number with the verb.
It is usually a person, an animal or a thing who performs this action. There are the following types of subjects in a sentence:
- Express subject
- Tacit subject
- Undetermined subject
In this case the organizers of the event are the ones who were unhappy, that's why they are the subject.