Which of the following statements about parasitism is correct?

The parasite and host tend to co-evolve, developing resistance and counter-resistance mechanisms.

 The correct answer is Option (3) - The parasite and host tend to co-evolve, developing resistance and counter-resistance mechanisms.

Parasitism: Parasitism is a relationship between two living organisms of different species in which one organism called parasite obtains its food directly from other living organism called host. Many parasites have evolved to be host-specific (they can parasitise only a single species of host) in such a way that both host and the parasite tend to co-evolve; that is, if the host evolves special mechanisms for rejecting or resisting the parasite, the parasite has to evolve mechanisms to counteract and neutralise them, in order to be successful with the same host species. Cuscuta, a parasitic plant that is commonly found growing on hedge plants, has lost its chlorophyll and leaves in the course of evolution. It derives its nutrition from the host plant which it parasitises.