Q: Q: What is the main sex hormone in males called? A: | OPTIONS:
- estrogen
- caffeine
- methane
- testosterone
A: testosterone

Q: Q: What do aquatic mollusk species use for respiration? A: | OPTIONS:
- lungs
- phototropism
- pores
- gills
A: gills

Q: Q: What kind of energy used heat from magma within the earth to heat homes or produce steam that turns turbines? A: | OPTIONS:
- thermal energy
- robust energy
- renewable energy
- geothermal energy
A: geothermal energy

Q: Q: Which organ system defends the body from pathogens and other causes of disease? A: | OPTIONS:
- digestion system
- nervous system
- respiratory system
- immune system
A: immune system