As shown in the chapter, scallops use jet propulsion to move from one place to another. Their shells make them denser than INT water, so they normally rest on the ocean floor. If a scallop wishes to remain stationary, hovering a fixed distance above the ocean floor, it must eject water so that the thrust force on the scallop is.

A. upward, upward

B. upward, downward

C. downward, upward

D. downward, downward