**Core Concept:** Hydatid disease is a zoonotic infection caused by the larval stage of Echinococcus granulosus, typically transmitted by dogs. The infection affects various organs, most commonly the liver and lungs.

**Why the Correct Answer is Right:**

A. The correct answer is "MC site is lung" because hydatid disease is primarily caused by the larval stage of Echinococcus granulosus, which primarily affects the lungs. The lungs are the most common site for initial infection, leading to the development of cysts.

B. Pre-op. Albendazole followed by surgery is the treatment of choice is partially correct. Albendazole is an antiparasitic drug that can help reduce the size of the cysts and prevent complications. Surgery is essential for definitive treatment, but preoperative albendazole administration can provide additional benefits.

C. 20% saline is scolicidal is incorrect. Scolecidal agents are substances used during liver hydatid cyst surgery to kill the parasite within the cyst. A more appropriate answer would be "20% hypertonic saline is used as a scolicidal agent."

D. Puncture, aspiration, injection, and respiration (PAIR) is done in hepatic hydatids refers to a surgical technique used for the management of liver hydatid cysts. The technique involves puncturing the cyst, aspirating the fluid, injecting an antiseptic solution to kill the parasite, and then applying pressure to prevent re-expansion of the cyst.

**Why Each Wrong Option is Incorrect:**

A. While the lungs are the most common site for initial infection, the correct answer should be "Hydatid cysts can form in various organs." Hydatid disease can affect other organs besides the lungs, such as the liver, spleen, kidney, and brain, among others.

C. 20% saline is not the correct scolicidal agent. Hypertonic saline (30% saline) is the appropriate scolicidal agent, while 20% saline may not be as effective in killing the parasite.

D. Puncture, aspiration, injection, and respiration (PAIR) is a surgical technique used for the management of liver hydatid cysts. This technique involves puncturing the cyst, aspirating the fluid, injecting an antiseptic solution (e.g., hypertonic saline) to kill the parasite, and then applying pressure to prevent re-expansion of the cyst.

**Clinical Pearls:**

Hydatid disease is a common zoonotic infection caused by the larval stage of Echinococcus granulosus, a tapeworm that inhabits the liver, lungs, and other organs. The infection is typically transmitted through ingestion of contaminated food or contact with infected dogs or other dogs' feces.

**Explanation:**

The correct answer is D: Puncture, aspiration, injection, and respiration (PAIR) technique is used for the management of liver hydatid cysts. This technique involves puncturing the cyst, aspirating the fluid to obtain a sample for diagnosis and