Water Carriers Compete to a Limited Degree with Motor Carriers

Water carriers compete to a limited degree with motor carriers. In most cases, what is the main interaction between the motor and water carriers?

A) to move shipments from one area at a port to another
B) to transport liquid cargo from a tanker to a refinery
C) to transport shipments too small for a barge to an area when they can be assembled into a large enough quantity for a barge
D) to overcome accessibility constraints of water carriers, linking inland areas to the waterways