What property do stem cells possess that makes them unique compared to other cells?

Stem cells are unique primarily due to their remarkable ability to differentiate into specialized cell types and their capacity to replicate indefinitely. This dual capability sets them apart from other types of cells in the body.

The ability to differentiate means that stem cells can develop into various specialized cells, such as muscle cells, nerve cells, or blood cells, depending on the signals they receive from their environment. This characteristic is crucial for growth, development, and repair of tissues.

In addition to differentiation, stem cells can replicate indefinitely. This means they can undergo numerous rounds of cell division without losing their stem cell properties. This self-renewal ability enables stem cells to maintain a consistent population within tissues throughout an organism's life.

In the context of this question, option D is correct because it encompasses both of these unique properties—indefinite replication and differentiation into specialized cell types.