Jan van helmont concludes that plants gain most of their mass from a. water b. the soil c. carbon dioxide in the air d. oxygen in the air (hurr)

Water

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The prevailing theory at the time was that plants grew by eating soil, and van Helmont devised a clever investigation to test this idea. He weighed a willow tree and weighed dry soil. He planted the tree, watered it and then left it for 5 years. He then re-weighed the tree, which had increased in mass by over 12 stone. He dried the soil and weighed it, showing that the soil was almost the same mass. He concluded that the tree grew by drinking water.

the answer is c. it will give up it's valence electron to the other atom.