Which one of the following stages in the life history of liver fluke infects the sheep ?

Options

A. Miracidium
B. Redia
C. Cercaria
D. Metacercaria

Answer

To determine which stage in the life history of the liver fluke infects the sheep, we can follow these steps:

### Step 1: Understand the Organism
The liver fluke is a type of flatworm that belongs to the phylum Platyhelminthes. It is known for being an endoparasite, which means it lives inside the body of its host.

**Hint:** Research the characteristics of flatworms and their classification in the animal kingdom.

### Step 2: Identify the Hosts
The liver fluke has a life cycle that involves two hosts. The primary host is the sheep, while the secondary or intermediate host is a freshwater snail.

**Hint:** Consider the roles of primary and secondary hosts in the life cycle of parasites.

### Step 3: Recognize the Life Cycle Stages
The liver fluke completes its life cycle through various stages. The key stages mentioned are:
- Miracidium: This stage infects the freshwater snail.
- Metacercaria: This is the stage that infects the sheep.

**Hint:** Look into the different stages of the liver fluke's life cycle and their respective hosts.

### Step 4: Determine the Infective Stage for Sheep
From the information gathered, it is clear that the liver fluke infects sheep during the Metacercaria stage.

**Hint:** Remember that the infective stage is the one that directly enters the host's body.

### Conclusion
Thus, the stage in the life history of the liver fluke that infects the sheep is the Metacercaria stage.

**Final Answer:** The correct answer is Metacercaria stage.