Q: These microorganisms are abundant in the human digestive track and serve many roles. what are they? A:

OPTIONS:
- antioxidants
- pathogens
- tumors
- bacteria

Answer: bacteria

Problem: OPTIONS:
- when the wind changes direction
- when the snow melts the ice caps
- when the ice and sand change directly into water vapors
- when the ice and snow change directly into water vapors
Q: Q: When does sublimation occur? A:
Answer: when the ice and snow change directly into water vapors

Problem:OPTIONS:
- air
- water
- food
- light

Q: Photosynthesis involves reactions that are dependent on what? A:
****
A: light

Q: What is the accumulated total of all the biochemical reactions occurring in a cell or organism called? A:
OPTIONS:
- respiration
- expansion
- circulation
- metabolism
metabolism

Q: Unstable isotopes give off particles and energy as what? A:
OPTIONS:
- electricity
- radiation
- ultraviolet light
- radioactivity

Answer: radioactivity

input with options: Q: Vertebrates differ from invertebrates because they lack this? A:
OPTIONS:
- legs
- head
- neck
- backbone or a spinal column
output:
backbone or a spinal column