Answer
(c) the 12th floor will have the greatest tangential speed.
Work Step by Step
The tangential speed is calculated by $v_T=r\omega$
The angular speed of the earth is constant and the same for everywhere on earth, so the difference in tangential speed depends on the distance away from the axis of rotation $r$.
The higher the floor of the building is, the farther it is from the axis of rotation, and $r$ will be greater. Therefore, (c) the 12th floor will have the greatest tangential speed.
