Final answer:
Robert L. Johnson's major achievement is that he became the first African American billionaire by creating the BET network, which he later sold to Viacom.
Step-by-step explanation:
Robert L. Johnson's major achievement is B. He became the first African American billionaire as creator of the BET network. Johnson founded the Black Entertainment Television (BET) network in 1980, which became a significant channel dedicated to African American audiences, offering a variety of entertainment and news programming.
In 2001, he sold BET to Viacom for approximately $3 billion, making him the first African American billionaire. His accomplishment is a testament to the success of black entrepreneurs and the impact of policies such as the establishment of the Office of Minority Business Enterprise (OMBE), which aimed to encourage and fund Black businesses.