## **Core Concept**
The Gray (Gy) is the SI unit of ionizing radiation dose, defined as the absorption of one joule of radiation energy per kilogram of matter. It measures the amount of radiation energy deposited in a mass of tissue, which helps in assessing the risk of radiation exposure.

## **Why the Correct Answer is Right**
One Gray (Gy) equals 100 rads, which is an older unit of measurement. The conversion factor is crucial for understanding and calculating radiation doses. The rad (radiation absorbed dose) is defined as the absorption of 100 ergs of radiation energy per gram of matter. Since 1 Gy = 1 J/kg and 1 J = 10^7 ergs, and considering 1 kg = 1000 grams, the conversion yields 1 Gy = 100 rads.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option suggests a conversion that does not align with the definition or standard conversion factors for radiation dose units.
- **Option B:** This option is incorrect because it does not accurately represent the relationship between Grays and another unit of radiation exposure or dose.
- **Option D:** This option is also incorrect as it misrepresents the conversion factor between Grays and rads or another relevant unit.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that 1 Sievert (Sv) equals 1 Gy for gamma radiation but Sv accounts for biological effect (radiation weighting factor). For X-rays and gamma rays, 1 Gy = 1 Sv. However, the question focuses on the physical dose, making **1 Gy = 100 rads** a critical conversion factor.

## **Correct Answer:** B. 100 rads