*Question*
Q: What do rocket-based systems use to propel itself into space? Choices: - water reactions - hydrogen reactions - nuclear reactions - chemical reactions A:
**Answer**
chemical reactions

*Question*
Q: Oysters require a certain minimum population density because they must be in close proximity to do this? Choices: - multiply - replicate - feed - reproduce A:
**Answer**
reproduce

*Question*
Q: How many mass distinctions have radically altered the history of life? Choices: - six - one - four - five A:
**Answer**
five

*Question*
Q: What is the basis of enzyme classification? Choices: - their shape - their color - their mass - reactions they catalyze A:
**Answer**
reactions they catalyze