The charge on X can be negative and that on Y negative.
TRUE if they can be repelling
The charge on X can be negative and that on Y positive.
TRUE if they can be attracting
The amount of charge on Y can be equal to that on X.
TRUE. The electrostatic forces on the spheres are going to be equal and opposite regardless of the magnitudes (Newton's Third Law). Therefore, the angle difference cannot be due to them having different charges.
The mass of X can be less than that of Y.
FALSE. Because Q < T, we know that the mass of X must be greater than the mass of Y. The fact that the angles are different tells us only about the masses (see the explanation immediately above). The horizontal components of the tensions in the strings must be equal. If the angles are different, it must be because the vertical components are different. To make Q smaller than T, it must have a greater vertical component for the same horizontal component.
The amount of charge on Y can be less than that on X.
You have a horizontal vector depending on the charge and a vertical vector depending on the weight, which we are mistakenly calling mass for this example. The horizontal force divided by the vertical force gives the tangent of the angle at which it hangs.
