A concave mirror is placed on a horizontal table with its axis directed vertically upwards. Let O be the pole of the mirror and C its centre of curvature. A point object is placed at C. It has a real image, also located at C. If the mirror is now filled with water, the image will be

Real, and will remain at C Real, and located at a point between C and ∞ Virtual and located at a point between C and O Real, and located at a point between C and O

Real, and located at a point between C and O