※ 다음 글을 읽고 물음에 답하시오. [문 18～문 19] Woodpeckers hit their heads against trees 12,000 times a day, but they don't get headaches. How is this possible? An American scientist, Ivan Schwab, found the answer. Woodpeckers' brains are protected by spongy bone that can ________ the shock from hitting their heads. Dr. Schwab also found why woodpeckers' eyes do not pop out. They have special eyelids that close a millisecond before each hit. Woodpeckers hit their heads against trees 12,000 times a day, but they don't get headaches. How is this possible? An American scientist, Ivan Schwab, found the answer. Woodpeckers' brains are protected by spongy bone that can ________ the shock from hitting their heads. Dr. Schwab also found why woodpeckers' eyes do not pop out. They have special eyelids that close a millisecond before each hit. 밑줄 친 부분에 들어갈 말로 가장 적절한 것은?