【单选题】

More than a hundred years ago, before theCivil War, a crew of cowboys stood outside a large horse corral, With them was their bossBradford Grimes, a cattleman, who owned a large South Texas ranch near the Gulf of Mexico.

Just then, Mrs. Grimes, the cattleman’s wife, came to the ranch house door and cried out, "Bradford!Bradford! ThoseBlacks are worth a thousand dollars apiece. One might get killeD、" The cowboys laughed, but they knew she was telling the truth. For they were allBlack slaves.Bradford Grimes was their owner.
Most of the firstBlack cowboys were slaves, brought by their masters from the old South. On the plantations in the South, the slaves cut cotton. On the ranches in Texas they had to learn a new trade—breaking horses and handling long-horns. Some were taught by Mexican vaqueros, some by Indiana who knew the ways of horses and cattle.
Grimes was only one of hundreds of slaveowning ranchers who ran cattle in Texas. The ranchers had brought their families and slaves from Mississippi, Georgia, and other southern states. They came on horseback, on foot, and in wagons.
Some ranchers settled near the Mexican border, but there they found that it was too easy for their slaves to escape.Even slaves as far north asAustin, the capital of Texas, came to think of Mexico as the promised lanD、As early as 1845, the year that Texas became a state, a Texas newspaper reported the escape of twenty-fiveBlacks. "They were mounted on some of the best horses that could be found, "the story said, "and several of them were well armeD、" Thousands of otherBlack slaves escaped in the same way.
All-Black cattle crews were common throughout central and eastern Texas. There were even a few freeBlacks who owned ranches before theCivil War.AaronAshworth was one of them, and he owned 2500 cattle, as well as some slaves of his own. He employed a White schoolmaster to tutor his children.Black cowboys helped to tame and settle a wild country.
Most of the firstBlack slaves that became cowboys ______.A．had been brought to Texas by their owners from the old south
B．came on their own to look for the promised land
C．came from ranches in Mexico looking for work on Texas cattle ranches
D．came fromAfrica