Final answer:
The correct word to fill in the blank is 'That', making the sentence illustrate Alice Diaz's dedication by stating the noun clause as evidence of her devotion to her work.
Step-by-step explanation:
The correct option to complete the given sentence is (A) That. The sentence should read: That Alice Diaz was willing to work over the weekends to ensure the success of the ceremony is evidence of her devotion to her work. Here, "That" is used as a conjunction introducing a noun clause, which acts as the subject of the sentence, explaining the reason for her devotion. In contrast, 'But', 'Since', and 'After' are inappropriate because they do not introduce a noun clause in this context. For instance, 'Since' would imply a reason or cause, not the subject of the sentence.
Looking at Example 3 - Allen is scrambling to finish all of his projects, whereas Amy planned ahead and had everything finished by last Thursday - we see a comparison where 'whereas' is appropriately used to contrast Allen's and Amy's situations. However, in the question at hand, we need a word that makes the clause 'Alice Diaz was willing to work over the weekends to ensure the success of the ceremony' the subject of the sentence to describe her work ethic and dedication.