The correct option is B Grassland ecosystem
Pyramid of numbers is the sequential arrangement of the trophic level on the basis of the number of organism present at each level. In grassland, the producers, which are mainly grasses, are always maximum in number as compared to the primary consumers (herbivores) like rabbits, mice etc. are which are lesser in number than the grasses, the secondary consumers, snakes, and lizards are lesser in number than the rabbits and mice. Finally, the top (tertiary) consumers hawks or other birds are least in number. Thus, the correct answer is option B.