Q: What is an insect's hard outer exoskeleton made out of? Choices: - lectin - casein - melanin - chitin A:
chitin

Q: What element is released into the atmosphere by the burning of fossil fuels? Choices: - carbon - helium - oxygen - sulfur A:
sulfur

Q: Q: Most ecosystems are disturbed too often to attain what final, stable status? Choices: - undisrupted community - calm community - even community - climax community A:
A: climax community

Question: Q: What do we call a peptide hormone composed of nine amino acids that lowers blood pressure? Choices: - angiotensin - parcnid - bufotenin - bradykinin A:
Answer: bradykinin

*Question*
Q: One of the most advanced uses of what in medicine is the positron emission tomography scanner, which detects the activity in the body of a very small injection of radioactive glucose? Choices: - radionuclides - quarks - membranes - radioisotopes A:
**Answer**
radioisotopes

Q: Q: Different elements differ in the size, mass, and other properties of what fundamental structures? Choices: - ions - compounds - particles - atoms A:
A: atoms