Question: Q: The heart is a muscular organ that pumps blood through which system? Choices: - endocrine - pulmonary - nervous - circulatory A:
Answer: circulatory

Question: Q: Hydroelectric power harnesses the energy of what? Choices: - weather - heat - air - water A:
Answer: water

Question: Q: During what period on earth was coal formed? Choices: - Mesozoic - Neoproterozoic - Neoproterozoic era - the carboniferous period A:
Answer:
the carboniferous period