Pls help! on gregor mendel

P, F₁, and F₂

Explanation:

The parental generation is also known as P.  F₁ is the first generation and F₂ is the second generation.  

The top left is a nerve cell. They carry electrical impulses to the central nervous system.
They have branches(dendrons) which branch further as dendrites at each end. + provide a higher surface area.
They are covered in fat- acting as an electrical insulator.
They also have lots of mitochondria.

Hope this one helped :)