Correct Option: A

In the case of damage to human body due to radiation, the most important factor is the amount of the dose - the amount of energy actually deposited in the body. The absorbed radiation dose, the amount of energy absorbed per gram of body tissue, is usually measured in units called rads. Another unit of radation is the rem, or roentgen equivalent in man. For practical purposes, 1 rad (absorbed dose) = 1 rem or 1000 mrem (dose equivalent) (Source: United States Nuclear Regulatory Commission).