When handling cat litter, humans can potentially be exposed to a harmful single-celled protozoan. Its primary host is the common domestic cat, but it can also live in humans. This
protozoan is an example of a
predator
producer
parasite
scavenger

parasite

Explanation:

Toxoplasmosis is an infection caused by a single-celled protozoan parasite called Toxoplasma gondii, which usually affects warm-blooded animals, including humans. The infection is most commonly acquired from contact with cats and their feces or with raw or undercooked meat.

endo:

regulates body hormones, aldosterone, vasopressin

neural:

signal, regulates body using electric signals, reflex

endo has to do with hormones; aldosterone and vasopressin are both hormones. i also had this question and got it right : d