What Physical Effect Do Most Bridges Have on the Streams

What physical effect do most bridges have on the streams they cross?

A) They restrict flood flow on the floodplain, so water under the bridge is deeper and faster.
B) They minimize flooding upstream because the water upstream moves more slowly.
C) They decrease erosion under the bridge because they slow the water.
D) They decrease water level just downstream because the water there moves more slowly.
E) They cause vehicles crossing the bridge to get swept up in the flood.