The right option is; b. Pampas
Pampas is a not a savannah but a flat fertile grassland biome.
A savanna is a tropical grassland with trees that are widely spaced to avoid the closure of the canopy. Savannas cover about 20% of the earth's land area, and are associated with various types of biomes. Savannas have seasonal water availability, and its trees and grass are always green during the wet season. Examples of savannas are the African Serengeti, and Cerrado, the Brazilian savanna.