Problem:OPTIONS:
- matter
- earth
- soils
- dirt
- water
- wetland
- rocks
- erosion

You are presented with the quiz "Fossils are found in places that were previously covered in what?" But you don't know the answer, so you turn to your teacher to ask for hints. He says that "if fossils of a water animal or plant are found in a place then that place used to be covered by water in the past" and "common fossils include plant fossils like ferns". So, what's the best answer to the question?
****
A: water

Problem:OPTIONS:
- gold
- fibers
- white
- motors
- O3
- copper
- metal
- energy

You are presented with the quiz "what can wiring be made of?" But you don't know the answer, so you turn to your teacher to ask for hints. He says that "wiring requires an electrical conductor" and "gold is an excellent conductor of electricity". So, what's the best answer to the question?
****
A: gold

Problem:OPTIONS:
- skin
- appendages
- they bend
- eyes
- muscles
- sensory neurons
- organ
- insects

You are presented with the quiz "Some animals with jointed what have special excretory structures" But you don't know the answer, so you turn to your teacher to ask for hints. He says that "some arthropods have special excretory structures" and "arthropods contain jointed appendages". So, what's the best answer to the question?
****
A: appendages

Problem:OPTIONS:
- neurons
- insects
- viruses
- parasites
- rocks
- humans
- dirt
- mammals

You are presented with the quiz "What die quickly if their oxygen supply is cut off?" But you don't know the answer, so you turn to your teacher to ask for hints. He says that "brain cells die quickly if their oxygen supply is cut off" and "neurons are the nerve cells within the brain". So, what's the best answer to the question?
****
A:
neurons