Read the Following Scenario and Answer the Question Below

Read the following scenario and answer the question below.
In the early years of the 20th century there were lush stands of tall grasses in the valley on the east side of the Chiricahua Mountains in Arizona, stretching to Mexico on the south and New Mexico on the east. Dramatic summer rainstorms dumped huge amounts of water, very quickly, on the rocky upper slopes. The water ran down the slopes and into the grasslands, where it quickly soaked into the soft, porous soil where prairie dogs were active. Cattle ranching was in full swing, utilizing the rich grasses, but the ranchers did not appreciate the multitudes of prairie dogs that lived in the grasslands. Prairie dogs constantly dig through soil, making new burrows and eating grasses, roots and all. It was commonly believed that cattle would stumble in the prairie dog holes, break legs, and die of starvation. In addition, many ranchers were convinced that the prairie dogs would destroy the grasses because they directly competed with the cattle for food. The ranchers had already done away with most predators that might possibly affect cattle, and now they turned their attention to the prairie dogs. The ranchers became a part of a new federally sponsored movement to poison the grassland prairie dogs. This movement took root and spread through the 1920s and 1930s.
-In a previous chapter you read about "keystone species." How do the prairie dogs in this story meet the definition of a keystone species?

A) They don't meet the definition of a keystone species; the system did fine without them. The predators turned to cattle, and the grasses did better in the compact soil.
B) When the prairie dogs were removed, the cattle declined; this meets the definition of a keystone species.
C) Their burrows loosened the soil and served as homes for other species; they helped with nutrient recycling. They helped water infiltrate into the soil and kept soil loose for grass roots. When they were removed, the system deteriorated.
D) Their burrows caused cattle to break their legs and die. This made them directly responsible for the welfare of another species, which meets the definition of a keystone species.
E) The availability of prairie dogs kept the predators in check; when they were removed, the predator populations grew dramatically. They kept the soil aerated and compact.