Apopulation follows a period of a. decline; overshoot b. increase; scarcity c. scarcity; dieback

The right answer is B.

During the 20th century, the world population increased from 1.65 billion to 6 billion. In 1970, the world's population was half that of today.

In less than 15 years, 47% of the population will live in areas already under heavy water stress. In Africa, between 75 and 250 million people will face growing shortages in 2020 due to climate change. The scarcity of some arid and semi-arid regions will have a decisive impact on migration.

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.