2. which kind of nutrients cycle through the atmosphere?

Nutrient cycle is a process  of movement, reuse or recycling of nutrients in that particular environment. They are for both living and nonliving things, elements like carbon, oxygen are recycled through such cycles.

Nutrient cycle in an ecosystem involve:

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.

the answer is trees if i'm not mistaken