Statement I: Cuscuta, a parasitic plant that is commonly found growing on hedge plants, has lost its chlorophyll and leaves in the course of evolution.

Statement II: Parasites that feed on the external surface of the host organism are called ectoparasites.

Both statement I and II are correct .

 The correct answer is Option (3) - Both statement I and II are correct .

Statement I : Cuscuta, a parasitic plant that is commonly found growing on hedge plants, has lost its chlorophyll and leaves in the course of evolution. 

This statement is true. Cuscuta, commonly known as dodder, is a parasitic plant that lacks chlorophyll and leaves. Instead of photosynthesizing and producing its own food, it attaches itself to the stems of host plants and derives its nutrition by extracting nutrients and water from the host plant. Cuscuta has evolved specialized structures called haustoria that penetrate the host plant's vascular system to obtain these resources.

 Statement II : Parasites that feed on the external surface of the host organism are called ectoparasites.

This statement is true. Ectoparasites are parasites that live and feed on the external surface of the host organism. They do not invade the host's body but instead attach themselves to the skin, fur, feathers, or scales of the host. Examples of ectoparasites include lice, ticks, fleas, and mites. These parasites obtain their nutrients and complete their life cycles while remaining on the external surface of the host.