Final answer:
The sudden behavior of Tina not bringing her school materials can be described as 'apathy', which denotes indifference, unlike the other options that convey different emotions or actions.
Step-by-step explanation:
Tina's sudden lack of preparation for school could be described as apathy. The correct answer to fill in the blank in the sentence 'Tina did not even bother to bring a backpack or paper to school; her sudden ________________________ surprised and confused her teachers and friends.' would be 'a. Apathy'. Apathy represents a state of indifference or the lack of interest or concern. Considering the other options, euphoria is a feeling of great happiness, sympathy is sharing feelings of sadness with others, and a eulogy is a speech in praise of someone who has died. Therefore, 'apathy' correctly conveys the notion of indifference that Tina is demonstrating.