The illustration depicts five types of intercellular chemical signals. what kind of signal does "e" represent?

Hormones are the intercellular signal discharged into the blood by specific cells, they travel some distance in order to reach their target tissues and to perform other specific activities. Autocrine refers to the intercellular signals, which are discharged by the cells in a local area and affects the activity of the similar type of cell from which it was discharged.

Paracrine refers to the intercellular signals, which are discharged by the cells and influences other kinds of cells locally without being transported into the blood. Pheromones refer to the intercellular signals secreted into the surrounding and change the behavior and physiology of other individuals.

Neurohormones or neurotransmitters are the intercellular signals produced by the neurons. Of the mentioned intercellular signals, the "e" signifies neurotransmitter.

igneous rocks which formed by the crystallization of magma at the surface of the earth called extrusive rocks. they are characterized by fine-grained textures because the rapid cooling at or near the surface did not provide enough time for large crystals to grow.