In the leaf disk assay, why did the leaves go back down after being placed in the dark?
Options:
A. Photosynthesis stopped, thus when oxygen was used by cellular respiration, the leaves lost their air pockets and became more dense.
B. Photosynthesis started, thus when oxygen was used by cellular respiration, the leaves lost their air pockets and became more dense.
C. Photosynthesis stopped, thus when carbon dioxide was used by cellular respiration, the leaves lost their air pockets and became more dense.
D. Photosynthesis stopped, thus when oxygen was used by cellular respiration, the leaves lost their air pockets and became less dense.