Sentence A's use of a semicolon is meant to show a connection between two different ideas. Sentence B's use of the colon is used to precede a list or explanation.
<span> Marian Anderson was 42 when she sang her legendary open-air concert at the Lincoln Memorial on 9 April 1939.
2.
Anderson was a famous contralto of the day, and the concert was
arranged after the Daughters of the American Revolution refused to let
her perform at Constitution Hall because she was black
3. (First Lady Eleanor Roosevelt resigned from the DAR in protest and helped arrange the concert at the Lincoln Memorial.)
4. Anderson was the aunt of Oregon Symphony conductor James DePriest
5.
On January 7, 1955, Anderson broke the color barrier by becoming the
first African-American to perform with the New York Metropolitan Opera.
6.
In 1958 she was officially designated delegate to the United Nations, a
formalization of her role as "goodwill ambassador" of the U.S. she
played earlier, and in 1972 she was awarded the UN Peace Prize.
7.
On January 27, 2005, a commemorative U.S. postage stamp honored Marian
Anderson as part of the Black Heritage series. Anderson is also pictured
on the US$5,000 Series I United States Savings Bond</span>
