**Core Concept**
Hydatid cyst of the liver, also known as hepatic echinococcosis, is a parasitic infection caused by the larval stage of the Echinococcus granulosus tapeworm. This condition results from the ingestion of contaminated food or water, leading to the development of a cystic lesion in the liver.

**Why the Correct Answer is Right**
The correct answer is b) In 80% cases cyst is single. This is because the majority of patients with hepatic echinococcosis present with a solitary cystic lesion in the liver. The cysts can be located in various parts of the liver, but single lesions are more common. The presence of a single cyst does not necessarily imply a simple infection, as the cysts can have multiple compartments and may contain daughter cysts.

**Why Each Wrong Option is Incorrect**
* **Option A:** Caused by E. granulosus - This statement is correct, but option b is also correct, making this option redundant and not the best choice.
* **Option C:** Blood culture helpful - Blood cultures are not typically helpful in diagnosing hydatid cysts of the liver, as the infection is caused by a parasitic organism that is not usually detectable in the blood.
* **Option D:** Surgery is the only treatment - While surgical intervention is often necessary to treat hydatid cysts of the liver, it is not the only treatment option. Other treatments, such as paclitaxel injection, may be used for certain cases.

**Clinical Pearl / High-Yield Fact**
It is essential to note that hydatid cysts of the liver can have a variable presentation, and the diagnosis may be challenging. A high index of suspicion is required, and imaging studies, such as ultrasound or CT scans, are essential for diagnosing this condition.

**Correct Answer: B. In 80% cases cyst is single.**