, produced by stem cells found in bone marrow , manufacture antibodies used to counter the effects of antigens. A.) T-Cells
B.) B-Cells
C.) Macrophages
D.) A- Cells

B cells develop into plasma cells that make antibodies to fight infection.

the supermassive black hole is in the middle of the galaxy.

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.