The difference between two roots of the equation $x^3-13x^2+15x+189=0$ is 2. Then the roots of the equation are :

Question

\[\begin {array} {1 1} (a)\;-3,5,7 & \quad (b)\;-3,-7,-9 \\ (c)\;3,-5,7 & \quad (d)\;-3,-7,9 \end {array}\]