单项选择题

At Denver there was a flow of passengers into the coaches on the eastbound express. In one coach there sat a very pretty young woman dressed in elegant taste and surrounded by all the comforts of an experienced traveler. Among the newcomers were two young men, one of handsome look with a bold, frank expression; the other heavily built and roughly dressed. The two were handcuffed together.
As they passed down the aisle of the coach the only vacant seat offered was the one facing the attractive young woman. Here the linked couple seated themselves. When the young woman’s glance fell upon them, her face brightened with a lovely smile.
"Well, Mr. Easton, if you will make me speak first, I suppose I must. Don’t you ever recognize old friends when you meet them in the west"
The young man roused himself sharply at the sound of her voice, seemed to struggle with a slight embarrassment which he threw off instantly, and then clasped her fingers with his left hand.
"It’s Miss Fairchild," he said, with a smile. "I’ll ask you to excuse the other hand; it’s otherwise engaged just at present."
He slightly raised his right hand, bound at the wrist by the shining "bracelet" to the left one, of his companion. The glad look in the girl’s eyes slowly changed to a puzzled horror. The glow faded from her cheeks. Easton, with a little laugh, as if amused, was about to speak again when the other stopped him. The heavily-built man said, "You’ll excuse me for speaking, miss, but, I see you’re acquainted with the marshal here. If you’ll ask him to speak a word for me when we get to prison, he’ll do it, and it’ll make things easier for me there. He’s taking me to Leavenworth prison. It’s seven years for making fake money."
"Oh!" said the girl, with a deep breath and returning color. "So that is what you are doing out here A marshal!"
The conversation between the girl and Easton carried on happily until the heavily-built man growled, "Say, Mr. Marshal, this isn’t quite fair. I’m needing a drink, and haven’t had a smoke all day. Haven’t you talked long enough Take me in the smoker now, won’t you I’m half dead for a pipe."
When the two men left for the smoker, said one of the passengers near by: "That marshal’s a good sort of guy. Some of these Western fellows are all right."
"Pretty young to hold an office like that, isn’t he" asked the other.
"Young!" exclaimed the first speaker, "Why—Oh! didn’t you catch on Say—did you ever know an officer to handcuff a prisoner to his right hand" When the young woman saw the two men, she smiled at them because ______.