Q: The first line of defense includes mechanical, chemical, and which other barrier? Choices: - independent - physical - surgical - biological A:
biological

Q: An element symbol without a charge written next to it is assumed to be what? Choices: - dead atom - corroborate atom - surfactants atom - uncharged atom A:
uncharged atom

Q: Q: The nitrogen that enters living systems by nitrogen fixation is successively converted from organic nitrogen back into nitrogen gas by what? Choices: - algae - pollen - viruses - bacteria A:
A: bacteria

Question: Q: Skeletal muscles must work in pairs to move bones back and forth at a joint because they can only do what? Choices: - vibrate - pull - expand - contract A:
Answer: contract

*Question*
Q: When fuel is burned, most of the energy is released in what form? Choices: - precipitation - carbon dioxide - humidity - heat A:
**Answer**
heat

(Question)
Q: What forms when cells start to grow out of control? Choices: - fat - moles - inflammation - tumor A:
(Answer)
tumor