A gardener lists everything a leaf is supplied with before it can build sugar. Which pair are the raw materials that photosynthesis actually uses up?

Explanation

The reaction combines a gas absorbed from the air with water taken from the soil, so those are the two substances consumed as it runs. Mineral ions are absorbed by the plant as well, but they have other jobs and are not consumed in the reaction that builds sugar, and the gas a leaf gives off is made by the reaction rather than fed into it.