19. 밑줄 친 (A), (B)에 들어갈 말로 가장 적절한 것은?(순서대로 (A), (B))

When an organism is alive, it takes in carbon dioxide from the air around it. Most of that carbon dioxide is made of carbon-12, but a tiny portion consists of carbon-14. So the living organism always contains a very small amount of radioactive carbon, carbon-14. A detector next to the living organism would record radiation given off by the carbon-14 in the organism. When the organism dies, it no longer takes in carbon dioxide. No new carbon-14 is added, and the old carbon-14 slowly decays into nitrogen. The amount of carbon-14 slowly    (A)    as time goes on. Over time, less and less radiation from carbon-14 is produced. The amount of carbon-14 radiation detected for an organism is a measure, therefore, of how long the organism has been    (B)   . This method of determining the age of an organism is called carbon-14 dating. The decay of carbon-14 allows archaeologists to find the age of once-living materials. Measuring the amount of radiation remaining indicates the approximate age.

• 1
   decreases, dead
• 2
   increases, alive
• 3
   decreases, productive
• 4
   increases, inactive