Experiment on carbon dioxide is necessary for photosynthesis

Lime water absorbs carbon dioxide and hence there is no carbon dioxide for the leaf and hence photosynthesis does not take place and no starch is prepared. Hence on iodine test, the presence of starch is negative and thus proves that carbon dioxide is required for photosynthesis.

the answer is b)3/8x+1

because photosynthesis could not occur (apex)