**Question:** Dose of acute radiation causing permanent sterility in males is

A. 0.5 Gy
B. 1 Gy
C. 2 Gy
D. 5 Gy

**Core Concept:**
Acute radiation syndrome is a condition caused by a rapid exposure to high doses of ionizing radiation. Permanent sterility is one of the long-term effects of radiation exposure on the male reproductive system.

**Why the Correct Answer is Right:**
The correct answer is **D** 5 Gy (Gray), which represents the dose of acute radiation exposure leading to permanent sterility in males. This threshold is considered the minimum dose required to cause irreversible damage to the reproductive system, including the testes, which are essential for sperm production and male fertility.

**Why Each Wrong Option is Incorrect:**
A. 0.5 Gy is too low to cause permanent sterility, as it represents a much lower dose than the required threshold for testicular damage.
B. 1 Gy is still lower than the required dose for permanent sterility, although it may cause temporary infertility due to radiation-induced inflammation and oxidative stress.
C. 2 Gy is higher than the correct dose but still not high enough to cause permanent sterility, as the testicular damage may be reversible under proper medical intervention and recovery.

**Clinical Pearl / High-Yield Fact:**
Radiation exposure should be minimized during diagnostic or therapeutic procedures, as even low doses of ionizing radiation can cause temporary or permanent sterility and other harmful effects on male reproductive health. Proper radiation protection measures and counseling of patients about the potential risks are crucial.