Select the option that correctly replaces the underlined portion of the given sentence:

She is confident to win the championship.

Correct Answer: of winning the championship

Explanation:

1. Grammatical Rule: The adjective confident takes the preposition of (or about) followed by a gerund (a verb ending in -ing acting as a noun). The correct standard structure is: confident + of + [verb]-ing.

2. Analysis of the Original Sentence: In the sentence "She is confident to win the championship," using the infinitive form "to win" after the adjective confident is grammatically incorrect.

3. Finding the Correct Replacement: Replacing "to win" with the prepositional phrase "of winning" makes the sentence grammatically accurate and idiomatic: "She is confident of winning the championship."

Therefore, the correct option to replace the underlined portion is of winning the championship.