The infected stage of Ascaris is
A. Egg
B. Fourth Juvenile
C. Second Juvenile
D. Adult worm itself
C. Second Juvenile
The infected stage of Ascaris is the A. Egg stage.
The infected stage of Ascaris is the adult worm itself, which means the correct answer is D.
Now, let me explain how to arrive at this answer. Ascaris, also known as the roundworm, goes through several stages in its life cycle. Understanding this life cycle can help us identify the infected stage.
1. Egg: Ascaris eggs are passed in the feces of an infected person into the environment.
2. First juvenile stage: Inside the egg, the larvae develop and become infective.
3. Second juvenile stage: When a person ingests the infective eggs, the larvae hatch in the small intestine and penetrate the intestinal wall. From there, they migrate through the bloodstream to the lungs.
4. Fourth juvenile stage: In the lungs, the larvae mature further, break into airways, are swallowed, and return to the intestines.
5. Adult worm: Once back in the intestine, the larvae develop into adult worms, reaching lengths of up to 30 centimeters.
It is important to note that the infection stage refers to the stage at which the parasites can cause disease or harm to their host. In the case of Ascaris, it is the adult worm stage that causes infection and leads to symptoms in the human host. So, the correct answer is D. Adult worm itself.