Q: Why do comet tails always point away from the sun instead of trailing behind the comet? Choices: - dust particles attract - dust particles evaporate - dust particles liquify - dust particles recoil A:
dust particles recoil

Q: Another measure of the effectiveness of a machine is its what? Choices: - aesthetic effect - cost benefit - chemical advantage - mechanical advantage A:
mechanical advantage

Q: How are protozoa that cause giardiasis spread? Choices: - insects - starch and water - lakes and rivers - food and water A:
food and water