In the 1660s, flemish physican jan van helmont grew a small willow tree in a pot of soil. He added only water to the pot. At the end of five years, he found that the tree had gained 75 kilograms, but there was very little change in the mass of the soul. Van helmont concluded that the plan gianed weight directly from the water. We now know that his conclusion is only partially correct because, in addition to water, photosynthesis also requires


a. oxygen from the atmosphere

b. carbon dioxide from the atmosphere

c. proteins from animal prey

d. carbohydrates from the soil