The bacteriophage that resembles a tadpole is the T-even phage, such as the the T2, T4, and T6 phages. These phages have a distinct structure consisting of a large polyhedral head attached to a long, slender tail. The head contains the viral DNA, while the tail serves as a tubular structure used to inject this genetic material into the bacterial host. When viewed under an electron microscope, this head-and-tail arrangement closely resembles the body and tail of a tadpole, which is why they are described in this way. This unique morphology not only gives them their characteristic appearance but also plays a crucial role in their infection cycle, as the head stores genetic information and the tail enables attachment and DNA transfer into the host bacterium.

T₂ bacteriophage does have a head and tail structure, but it does not resemble a tadpole as closely as T₄ does.

This is the correct option, as the T4 bacteriophage has a head and a contractile tail, resembling a tadpole.

This option is incorrect, as only the T4 bacteriophage resembles a tadpole structure.

This option is incorrect, as the T4 bacteriophage is the correct answer.