A bluff is cliff or hill with a broad, steep face. The question though does not ask one to focus on the bluffs but rather the area between them. Look at the gradient of the land between the two points given. The lack of contour lines means it is quite flat. As well, notice that there is a river flowing through this location with a pronounced meander. The best answer is (B) - a flood plain.

There is no oxbow lake (C) shown between the two points given and it is too small to be considered an entire drainage basin (D). Peneplain (A) means "almost a plain" and is formed when interfluves (i.e. the higher land between two valleys in the youthful stage of a river) have been worn down to almost a level surface.