3. How do osteoclasts break down the bone?
A. Using stress
B. Using enzymes and acids
C. Using minerals
D. Osteoclasts do not break down the bone

4. The reasons astronauts must constantly exercise in orbit is due to
A. Excess of nutrients
B. Excess of osteoblasts
C. Lack of nutrients
D. Lack of skeletal strain in free fall

5. In order for bones to be strong enough to carry weight, for instance, they need to
experience during their growth process.
A Humidity
B. Right temperature
C. Real stress

6. Explain Wolf's Law. Why is it so important to understand changes that happen in astronauts
bones in space?