Choose the correct answer: Three point charges are placed at the corners of an equilateral triangle. Assuming only electrostatic forces are acting (a) The system can never be in equilibrium (b) The system will be in equilibrium if the charges rotate about the centre of the triangle (c) The system will be in equilibrium if the charges have different magnitudes and different signs (d) The system will be in equilibrium if the charges have the same magnitudes but different signs