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Across 4. any of the pieces of hard whitish tissue making up the skeleton in humans and other vertebrates. 6. we breathe it in and keeps us alive 7. having well-developed muscles. 10. able or likely to shatter violently or burst apart. 15. of a system or machine achieving maximum productivity with minimum wasted effort or expense. 18. a strict ray of food that is healthy 19. a hollow muscular organ that pumps the blood through the circulatory system by rhythmic contraction and dilation 20. relating to or denoting exercise taken to improve the efficiency of the body's cardiovascular system in absorbing and transporting oxygen.

Down 1. being fast in time and can run fast 2. the red liquid that circulates in the arteries and veins of humans 3. a point at which parts of an artificial structure are joined. 5. the organization of the different elements of a complex body or activity so as to enable them to work together effectively. 8. successfully bring about or reach a desired objective or result by effort, skill, or courage. 9. the condition of being protected from or unlikely to cause danger, risk, or injury. 11. a pain that occurs in any part of the body 12. something done, felt, or thought in response to a situation or event. 13. a flavorous subsense that comes from a tap 14. we use it to measure how long it takes to do something 16. being healthy and can run ect 17. a hurt that happens in the body