Carbon dioxide is passed into a solution of bromothymol blue indicator until the acid solution turns yellow. A sprig of elodea is then placed into this yellow solution. After a few hours in the sunlight, the yellow solution turns blue. The purpose of this experiment is to show that
(A) oxygen is given off during photosynthesis
(B) carbon dioxide is used during photosynthesis
(C) carbon dioxide is given off as a by-product of photosynthesis
(D) bromthymol blue changes to bromthymol yellow under acid conditions
(E) chlorophyll acting as a photocatalyst is necessary for photosynthesis
Answer: B