Yes Carbon dioxide is necessary for photosynthesis because Photosynthesis didn't go on because there was no Carbon dioxide in flask X.
The carbon dioxide was absorbed by the sodium hydroxide. In flask Y, the colour of the iodine solution turned blue black. This is because starch was present in the leaf of flask Y. Starch was present because it underwent photosynthesis.
Blue light bends more.
The laser would miss and you would need to aim below the fish.
He would become shaky and his heart would begin to race/thump.
