What two hormones are secreted from the same gland but oppose the action of one another?

the calvin cycle has three stages. in stage 1, the enzyme rubisco incorporates carbon dioxide into an organic molecule. in stage 2, the organic molecule is reduced. in stage 3, rubp, the molecule that starts the cycle, is regenerated so that the cycle can continue

i think it would be b. tissue because an organ system is a group of organs that work together to perform one or more functions. each does a particular job in the body, and is made up of certain tissues.