Which of the following words/phrases best replaces the word “enrolled” in sentence 6?

Directions: The following passage is an early draft of an essay. Some parts of the passage need to be rewritten. Read the passage and select the best answer for the question that follows. Keep in mind that some questions are about particular sentences or parts of sentences and ask you to improve sentence structure or word choice. Other questions ask to consider organization and development. In choosing the answer, follow the requirements of standard written English.

[1] Towards the ending of the summer of 1917 it was being very hot in New York, and hotter still aboard the transatlantic liner. [2] One glance at our cabins, at the crowded decks and the dining-room, sufficed to bring home to us that the days of luxurious sea travel, of a la carte restaurants, and Louis Seize bedrooms were gone - at least for a period. [3] The prospect of a voyage of nearly two weeks was not enticing. [4] The ship, to be sure, was far from being the best of those still running on a line which had gained a magic reputation of immunity from submarines; three years ago she carried only second and third class passengers! [5] But most of us were in a hurry to get to the countries where war had already become a grim and terrible reality. [6] In one way or another we had all enrolled. [7] The first welcome discovery among the crowd wandering aimlessly and somewhat disconsolately about the decks was the cheerful face of a friend whom at first I did not recognize because of his amazing disguise in uniform. [8] He had been associated in my mind with dinner parties and clubs. [9] That life was past. [10] He had laid up his yacht and joined the Red Cross and, henceforth, for an indeterminable period, he was to abide amidst the discomforts and dangers of the Western Front. [11] The likewise cheerful members of a group whom I found gathered by the after rail were similarly attired. [12] Two well-known specialists from the Gens General Hospital made significant contributions to serve the people of France which was almost doctorless. [13] When I reached France it seemed to me that I met all the celebrated medical men I ever heard of. [14] A third in the group was a business man from the Middle West who had wound up his affairs and left a startled family in charge of a trust company. [15] Though his physical activities had hitherto consisted of an occasional mild game of golf, he wore his khaki like an old campaigner; and he seemed undaunted by the prospect - still somewhat remotely ahead of him - of a journey across the Atlantic to the active war zone.