1. What is the name of the tough, flexible protein found in connective tissue that provides strength and elasticity to skin, tendons, and ligaments?

• Keratin
• ✓ Collagen
• Elastin
• Fibrin

2. Which layer of Earth's atmosphere is where most weather occurs and temperature decreases with altitude?

• Stratosphere
• Mesosphere
• ✓ Troposphere
• Thermosphere

3. What is the chemical symbol for sodium?

• So
• ✓ Na
• Sd
• S

4. How many pairs of chromosomes are present in a typical human cell nucleus?

• ✓ 23 pairs
• 46 pairs
• 26 pairs
• 13 pairs

5. In quantum mechanics, which principle states that it is impossible to simultaneously know both the exact position and exact momentum of a particle?

• Pauli Exclusion Principle
• ✓ Heisenberg Uncertainty Principle
• Planck's Constant
• Schrödinger's Paradox