The article states:
In the 1100s, Arabian and Turkish warriors rode steeds in circles while tossing a ball back and forth. They weren't just horsing around, however. The point was to prepare them for battle by improving their equestrian skills, or horseback riding abilities. The training exercise spread to Europe, where it was practiced by knights.
Which phrase from the passage helps you understand the meaning of the word equestrian?
A.to prepare them
B.practiced by knights
C.tossing a ball
D.horseback riding abilities