Where the land is flat, exerts a minimal influence on topographic development. where the land is flat, exerts a minimal influence on topographic development. gravity water mechanical weathering chemical weathering biological weathering?

The correct answer is - gravity.
The gravity with it's pulling force puts pressure on the objects by pulling them downwards, which with the help of few other factors makes the objects break and fall, and thus change the relief forms. But this is only when there's something in a position that means that it can fall downwards, but this is lacking on a flat land because there's nowhere where the object can be pulled and fall down.