Which of the following cells is the most sensitive to radiation?

White blood cells are particularly sensitive to radiation due to their role in the immune system and their relatively high turnover rate compared to other cell types. These cells are part of the body's defense mechanism and are constantly regenerating, making them more susceptible to damage from ionizing radiation.

When radiation exposure occurs, it can lead to disruptions in cell division and function, especially in rapidly dividing cells, which includes many types of white blood cells. This susceptibility is due in part to their role in producing antibodies and responding to infections, which requires them to be in a state of constant readiness and replication.

In contrast, red blood cells, while also affected by radiation, have a longer lifespan and are not as rapidly turned over as white blood cells. Muscle cells and nerve cells have slower rates of division and regeneration, making them less sensitive to the immediate effects of radiation compared to the active and rapidly dividing white blood cells. Thus, white blood cells emerge as the most radiation-sensitive cells in the body.