To determine which statements are correct, let's analyze each one:$\\$(a) Centre of mass of a body always coincides with the centre of gravity of the body.$\\$• This statement is not always true. The center of mass and center of gravity coincide only when the gravitational field is uniform across the body. In non-uniform fields, they may not coincide.$\\$(b) Centre of mass of a body is the point at which the total gravitational torque on the body is zero.$\\$• This statement is true. The center of mass is the point where the total gravitational torque is zero, meaning it is the balance point of the body under gravity.$\\$(c) A couple on a body produces both translational and rotational motion in a body.$\\$