A stands out most to me, CO comes from the air and air is basically oxygen we breath. When we exhale CO comes out (of course). I would say A is correct.
The stem of the plant should be cut at least three to four inches above the surface level. The glass capillary should be tightly fixed with the stem. The initial water level and the final water level should be carefully noted. The droplets on the leaves should be observed and conclude that these drops are not from transpiration.
When the reactants are heated, the average kinetic energy of the molecules increases. This means that more molecules are moving faster and hitting each other with more energy.
