Consider two cylindrical rods of identical dimensions, one of rubber and the other of steel. Both the rods are fixed rigidly at one end to the roof. A mass M is attached to each of the free ends at the centre of the rods. Then, [NCERT Exemplar] 

the steel rod will elongate and change shape but the rubber rod will only elongate

both the rods will elongate but there shall be no perceptible change in shape

the steel rod will elongate without any perceptible change in shape, but the rubber rod will elongate and
the shape of the bottom edge will change to an ellipse

the steel rod will elongate without any perceptible change in shape, but the rubber rod will elongate with
the shape of the bottom edge tapered to a tip at the centre