[单选题]
A ball is thrown with a velf(8iome s :ei17a3av rocity o0ar3p4wuto/8 vzwi44zqn, r ef 20 m/s at an angle of 60e above the horizontal. What is the horizon0nrzvpwq3,az44 i to e/48rw utal component of its instantaneous velocity at the exact top of its trajectory?
