Problem: OPTIONS:
- carbon bond
- Ionic bond
- radiation bond
- chemical bond
Q: Q: What bond is a force of attraction between ions and atoms? A:
Answer: chemical bond

Problem:OPTIONS:
- stress fracture
- rheumatism
- osteoporosis
- osteoarthritis

Q: What occurs when the cartilage at the ends of the bones breaks down? A:
****
A: osteoarthritis

Q: What thin whip-like structures help prokaryotes move toward food or away from toxins? A:
OPTIONS:
- sporangia
- cilia
- antennae
- flagella
flagella

Q: What are the "levels" in a food chain or web called? A:
OPTIONS:
- parts
- root
- gauges
- trophic

Answer: trophic

Question: Q: What type of mammals includes opossums, kangaroos, and koalas? A:
OPTIONS:
- crustaceans
- arthropods
- monotremes
- marsupials
Answer: marsupials

input: OPTIONS:
- liver
- steel
- bark
- skin Now, answer this question: Q: The outer layer of what anatomical structure is so tough that it keeps out most pathogens? A:
A:
output:
skin