Which of the following statements are correct? 

(1) Centre of mass of a body always coincides with the centre of gravity of the body.
(2) Centre of mass of a body is the point at which the total gravitational torque on the body is zero.
(3) A couple on a body produces both translational and rotational motion in a body.
(4) Mechanical advantage greater than one means that small effort can be used to lift a large load.

Centre of gravity of a body is the point at which the total gravitational torque on body is zero. Centre of mass and centre of gravity coincides only for symmetrical bodies. Hence statements (1) and (2) are incorrect. A couple of a body produces rotational motion only. Hence statement ( 3) is incorrect. Mechanical advantage greater than one means that the system will require a force that is less than the load in order to move it. Hence statement ( 4 ) is correct.

NOTE :  In original question paper options for this question were (a)   (1) and (2)    (b)  (2) and (3)        (c)  (3) and (4)    (d )  (2) and (4)
None of the given options is correct. 

Hence option (4) is modified and made the correct option