I think tissue or a nucleus
Hormones are a group of chemicals released by exocrine glands

These hormones are directly secreted into bloodstream from where they reach the site.
Because if we use too much coal we are wasting fossil fuels and burning coal hurts the environment so the alternative energy sources provide clean energy
Answer:
cell membrane
Explanation
It's the outer living boundary of animal cells. It's made of lipid and protein. Plasma Membrane is a mosaic of phospholipids, cholesterol, and proteins, the proteins in plasma membrane regulates the coming/going of substances into/out of the cell.
The general term of it all is Cytology, which means the study of the cells. This in turn is split into smaller sciences like Cytophysiology (Study of cell physiology and anatomy), Ctyopathology (Study of diseases effects on cells), and Cytochemistry (study of cell biochemistry).