Problem:OPTIONS:
- rock metamorphizing
- a hydraulic system
- Time and energy
- the ground shaking
- Temperature
- one celled organisms
- chemical reaction
- flow of electrons

You are presented with the quiz "What can change the remains of prehistoric living things into natural gas?" But you don't know the answer, so you turn to your teacher to ask for hints. He says that "heat and pressure change the remains of prehistoric living things into natural gas" and "heat and pressure cause a rock to metamorphize". So, what's the best answer to the question?
****
A: rock metamorphizing

Problem:OPTIONS:
- the environment
- people
- rocks
- bacteria
- humans
- alligators
- parasites
- plants

You are presented with the quiz "What may compete for territory, water, food, or mates"" But you don't know the answer, so you turn to your teacher to ask for hints. He says that "animals may compete for territory, water, food, or mates" and "alligators are cold-blooded animals". So, what's the best answer to the question?
****
A: alligators

Problem:OPTIONS:
- their environment
- most cephalopods
- their ecosystem
- themselves
- coral reefs
- animals
- living things
- circulatory systems

You are presented with the quiz "Paralytic shellfish cause harm to what?" But you don't know the answer, so you turn to your teacher to ask for hints. He says that "poison causes harm to living things" and "poisoning is similar to paralytic shellfish poisoning ". So, what's the best answer to the question?
****
A: living things

Problem:OPTIONS:
- Proteins
- Enzymes
- oysters
- catabolism
- lungs
- ice cubes
- hair
- nutrients

You are presented with the quiz "what does the digestive system use to produce nutrients for the body?" But you don't know the answer, so you turn to your teacher to ask for hints. He says that "the digestive system breaks food into nutrients for the body" and "catabolism is the breaking down of food". So, what's the best answer to the question?
****
A:
catabolism