Consider the following statements regarding Serena Williams :
a. She is an American professional tennis player who is ranked No. 01 in women's
singles tennis.
b. She became the world No. 01 for the first time on July 8,2002.
c. She has won four Olympic gold medals.
d. In December 2015, she was named Sportperson of the Year by the Sports
Illustrated magazine.
Which of the statements given above are correct ?