Why are children particularly sensitive to radiation?

Children are particularly sensitive to radiation primarily due to their longer life expectancy and the rapid division of their cells. This increased sensitivity is tied to a few key biological factors. First, children have many more years ahead of them where the potential risks associated with radiation exposure could manifest as long-term effects such as cancer. Secondly, their cells are more actively dividing, especially during periods of growth and development. Rapidly dividing cells are generally more susceptible to damage from radiation, which can lead to mutations and other harmful effects.

In contrast, the other options do not accurately reflect the reasons for increased sensitivity. For instance, while it might seem that having more developed organs could contribute to sensitivity, it is actually the opposite that is true – children's organs are still developing. Higher body mass and density are not relevant to radiation sensitivity, and being less cautious around x-ray equipment does not inherently increase biological sensitivity to radiation. Thus, the unique aspects of children's biological development underscore why option B is the correct answer in this context.