Answer:
Definition 5.
Step-by-step explanation:
During the school meeting, our class vice president contested the decision that the pep rally would be canceled due to the rain.
The given different definitions of the word "contest" reveal multiple uses of that word. Depending on the context, the word can be used to mean several things, all of which would refer to different aspects of that same word.
In the given sentence, the word 'contest" is used to mean "calling into question" or questioning the idea or in this case, the decision. This means that the "class vice president" questioned the decision of why the pep rally should be canceled. In other words, we can say the class VC asked why the pep rally have to be canceled.
Thus, the definition used is that of definition 5.