Question

The carbon that plants need for photosynthesis comes from
A.
carbon atoms from the breakdown of food.
B.
carbon dioxide gas in the atmosphere.
C.
carbon molecules dissolved in water.
D.
carbon molecules that the plant produces.

Answer 1

B. carbon dioxide gas in the atmosphere.

Plants take in CO2 through stomata and fix the carbon during the Calvin cycle in chloroplasts to make sugars (glucose).