You are presented with the quiz "What about an object can cause objects to be pulled towards planets?" But you don't know the answer, so you turn to your teacher to ask for hints. He says that "gravity pulls objects towards planets" and "an object's weight is the force of gravity on that object". So, what's the best answer to the question?
OPTIONS:
- phase
- structure
- Energy.
- means
- wind
- energy
- weight
- sunlight

Answer: weight

You are presented with the quiz "What happens when the immune system recognizes a foreign substance?" But you don't know the answer, so you turn to your teacher to ask for hints. He says that "antigens are molecules that the immune system recognizes as foreign to the body" and "antibodies are produced to fight antigens". So, what's the best answer to the question?
OPTIONS:
- an area swollen with pus
- The immune system fails
- irradiation
- Bacteria dies
- Antibodies are formed
- major threat to health
- Something that causes allergies
- Viruses reproduce

Answer: Antibodies are formed

You are presented with the quiz "What keeps mammals' metabolic rates high?" But you don't know the answer, so you turn to your teacher to ask for hints. He says that "mammals generate heat mainly by keeping their metabolic rate high" and "humans use food to generate body heat". So, what's the best answer to the question?
OPTIONS:
- gas
- muscle
- fur
- sleep
- water
- Fe
- food
- ice

Answer:
food