Which of the following words best completes the sentence?

She was _____ about the outcome of the test because she had studied very hard.

A. pessimistic

B. indifferent

C. confident

正解：confident

「confident」は「自信がある」という意味で、この文に最も適しています。「She was confident about the outcome of the test because she had studied very hard」は「彼女は一生懸命勉強したので、テストの結果に自信を持っていた」という意味です。他の選択肢「pessimistic（悲観的な）」、「indifferent（無関心な）」は文脈に合いません。