How do traits that are beneficial to organisms
increase in a population?
A. random mutations
B. DNA recognizes beneficial traits and
keeps them.
C. Natural selection "selects" those traits
over others.

C

Explanation:

Positive natural selection, or the tendency of beneficial traits to increase in prevalence (frequency) in a population, is the driving force behind adaptive evolution. ... At the molecular level, selection occurs when a particular DNA variant becomes more common because of its effect on the organisms that carry it.

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.