Which of the following organisms show radial symmetry?

Symmetry refers to the balanced arrangement of body parts or shapes around a central point or axis. It is one of the characteristic features that help us to classify an organism. 

If the body of an organism is cylindrical and has a central axis from which the body's parts radiate or are arranged in a regular fashion, the body will exhibit radial symmetry. Here, any plane passing through this central axis will divide the animal body into symmetrical halves. Radial symmetry can be seen in Hydra, starfishes, etc.

Amoebas and sponges have irregular body shapes hence they are asymmetrical.

Frog shows bilateral symmetry in which both lateral sides are symmetrical but the dorsal and ventral sides are non-symmetrical. This means that only one plane of symmetry will divide the entire animal into two equal halves.