At time \(t = 0\), rock \(A\) is released from rest from the top edge of a high vertical cliff of height \(H\). At the exact same instant and from the same height, rock \(B\) is launched horizontally with an initial speed \(v_0\). Air resistance is negligible. Which of the following describes the motion of rock \(B\) as observed in the reference frame of rock \(A\) while both rocks are in the air?