They are reactants because they are present before the reaction.
This biome has a layer of soil that can either be sandy, gravelly, or stony, depending on the type of desert. Deserts usually get at most 50 centimeters (20 inches) of rainfall a year, and the organisms that live in deserts are adapted to this extremely dry climate. Plants in deserts have adaptations to conserve water.
Pituitary gland ( insufficient production of STH )
A. Nutrients, vitamins would also be a correct answer