Which cells are more sensitive to radiation?

Rapidly dividing and young cells are indeed more sensitive to radiation due to several key factors.

First, rapidly dividing cells, also known as high turnover cells, are in a state of continuous division and are particularly vulnerable to radiation damage during the mitotic (cell division) phases. Radiation can disrupt DNA replication and cause cellular death, which is more likely to occur in cells that are actively dividing as compared to those that are not.

Young cells, typically defined as having not reached full maturity or differentiation, also possess an active metabolic state, making them more susceptible to the effects of radiation. These cells are often engaged in processes that can be easily disrupted by radiation, leading to significant harm or death.

In contrast to the correct choice, slowly dividing and old cells are generally more resistant to radiation. Old cells frequently show a reduced rate of division and may have completed their normal life cycle, thus exhibiting less sensitivity to radiation exposure. While there are exceptions, the primary tendency is that cell sensitivity to radiation increases with the rate of division and decreases with age, as the physiological processes and reparative mechanisms in older cells often become less efficient.