A tow of 9 barges is made up three abreast and three long. The towboat is faced up to the center string which is known as the __________.

Correct Answer: Option D — push string

In inland towing, the string of barges directly connected to the towboat's face wires is termed the push string. This configuration allows the towboat to exert direct control over the tow's heading and speed, facilitating efficient maneuvering and steering of the entire barge assembly through restricted waterways and channels.