单项选择题

TEXT B
The United States has a major racial problem on its hands. True, Britain is facing a similar problem, but for the time, being it is in America that it is graver. The only way to solve it is through education. Negroes should know about the contributions that black individuals and groups have made towards building America. This is of vital importance for their self-respect, and it is perhaps even more important for white people to know. For if you believe that a man has no history worth mentioning, it is easy to assume that he has no value as a man.
Many people believe that, since the Negro’s achievements do not appear in the history books, he did not have any. Most people are taken aback when they learn that Negroes sailed with Columbus, marched with the Spanish conquerors of South America and fought side by side with white Americans in all their wars. People are astonished when you tell them about Phillis Wheatley, who learned English as a slave in Boston and wrote first-class poetry. They have never heard of Benjamin Banneker, a mathematician and a surveyor, who helped to plan the city of Washington.
There has been a tendency all along to treat the black man as if he were invisible, little has been written about the 5,000 American Negroes who fought in the Revolution against the British, but they were in every important baffle. In the Anglo-American war of 1812, at least one out of every six men in the U. S. Navy was a Negro. In the Civil war, more than 200,000 black troops fought in the Union forces. How, then, did the image of the Negro as a valiant fighting man disappear To justify the hideous institution of slavery, slaveholders had to create the myth of the docile, slow- witted Negro, incapable of self-improvement, and even contented with his lot. Nothing could be further from the truth. The slave fought for his freedom at every chance he got, and there were numerous uprisings. Yet the myth of docility persisted.
There are several other areas where the truth has been twisted or concealed. Most people have heard of the Negro. Carver, who invented scores of new uses for the lowly peanut. But whoever heard of Norbert Rillieux, who in 1846 invented a vacuum pan that revolutionized the sugar-refining industry Or of Elijah McCoy, who in 1872 invented the drip cup that feeds oil to the moving parts of heavy machinery How many people know that Negroes are credited with inventing such different items as ice creams, potato chips, the gas mask and the first traffic light Not many. As for the winning the West, the black cowboy and the black frontiersman have been almost ignored, though film producers are becoming more aware of their importance. Yet in the typical trail crew of eight men that drove cattle from Texas to Kansas, at least two would have been Negroes. The black troops of the Ninth and Tenth Cavalry formed one-fifth of all the mounted troops assigned to protect the frontier after the Civil War. What difference does it make You may ask. A lot. The cowboy is the American folk-hero. Youngsters identify with him instantly. The average cowboy film is really a kind of morality play, with good guys and bad guys and right finally triumphing over wrong. You should see the amazement and happiness on black youngsters’ faces when they learn that their ancestors really had a part in all that.
According to the passage what is unknown to many people is that______