At the corners of a square, four particles having charges of the same magnitude are placed. If the electrostatic potential and field at the centre of the square due to these four charges is V and E respectively, then by suitably selecting the signs of the four charges of identical magnitude, which of the following conditions can be achieved?
1) $V=0,E=0$               2) $V=0,E\ne 0$             3) $V\ne 0,E=0$          4) $V\ne 0,E\ne 0$