Q: In gas exchange, oxygen flows into the blood, and what flows out? Choices: - naturally dioxide - carbon monoxide - liquid dioxide - carbon dioxide A:
carbon dioxide

Q: What colorful arc-shaped atmospheric phenomena are produced by a combination of refraction and reflection? Choices: - lightning - shadows - sunsets - rainbows A:
rainbows

Q: Most of the energy used by living things comes either directly or indirectly from what? Choices: - plants - the moon - the soil - the sun A:
the sun

Q: What form does formaldehyde take at room temperature? Choices: - solid - liquids - plasma - gas A:
gas