Within A Farewell to Arms, what would be the best definition of the word "regiments"?

The answer is B) Groups of battalions serving together under the command of a colonel.

The correct answer is, a Regiment is a unit in the Army. Specifically is a unit of forces on the ground that has battalions or units that support the Regiment and have their own headquarters.

"A Farewell to Arms" is a novel written by Ernest Hemingway that was published in 1929. The novel is located in Italy and Switzerland during World War I and refers to the war told by the Italian side. The main character is Frederick Henry, and he describes his life in the war and his affair with an English nurse called Catherine. He met the girls in Turin, Italy.