Finishing quickly is not as important as _____________ all the questions correctly.

The correct answer is "answering" because it is the gerund form of the verb, which functions as a noun in this context. The structure of the sentence indicates that what follows “as” should be a noun, and "answering all the questions correctly" fits that requirement. Gerunds, which are formed by adding -ing to the base form of a verb, can act like nouns, making them suitable for this construction.

Using "answer" would incorrectly suggest that you are referring to the action of answering in its base form rather than the process itself. "Answered" would imply a completed action, which doesn't fit as it would not convey the same meaning in this context. "Answers," on the other hand, is a noun but is plural and does not appropriately capture the ongoing action or process of addressing the questions correctly. Hence, "answering" is the most fitting choice.