Final answer:
We need more information to determine if the ball attracted by the negatively charged ebonite rod has a positive charge or is neutral and polarized. The correct answer is D.
Step-by-step explanation:
A suspended ball attracted by a negatively charged ebonite rod is not sufficient to conclude that the ball holds a positive charge. It could also be neutral and become polarized in the presence of the charged rod. According to principles of electrostatics, the correct answer is D: We need more information to make an inference.
When a charged object is brought near a conductor, such as the metal ball, it induces a polarization of the charges within the conductor, even if the conductor was initially electrically neutral. The side of the conductor nearest the charged rod will have an accumulation of opposite charges (positive in this case), and the side far away from the rod will have an excess of like charges (negative), creating an induced dipole. This induced positive charge on the nearest side is what contributes to the attraction. However, two neutral objects can also attract each other if they become polarized in the presence of each other.
If more information is provided, such as the behavior of the ball in the presence of a known charged object, one could make a definitive inference about the charge of the ball.