In which body system did scientists find the polio virus before it entered the nervous system?

The Digestive System

Explanation: Polio first enters the body through the mouth, usually through contact between people. The infected person can spread it through their nasal and oral secretions (mucous and saliva) as well as through their infected contaminated fecal matter (stool from bowel movement), in cases of lack of hygiene. Once the polio virus is in the digestive tract, it multiplies quickly, then enters the blood, and ends up in the nervous system. From there, it attacks the spine leading to paralysis.

i am positive it is c. condensing but i may be wrong

sheep is a herbivore animal whereas grasshopper belongs to the class chordates but both of them feed on greens.  

if grasshopper and sheep feeding on a pasture land, i do not think both of them will have any impact on each other. however, the number of the species can make difference. since sheep feed on greens, there is a possibility there left no pasture land for the grasshoppers or they may get extinct.