Which of the following are two main types of stem cells?

The two main types of stem cells are embryonic and adult stem cells.

Embryonic stem cells are derived from the early stages of embryos and have the unique ability to differentiate into any cell type in the body, meaning they are pluripotent. This characteristic makes them highly valuable for research and potential therapies for various conditions.

Adult stem cells, on the other hand, are found in specific tissues in the body and are multipotent, meaning they can differentiate into a limited range of cell types relevant to their tissue of origin. For example, hematopoietic stem cells from bone marrow can give rise to various types of blood cells.

In contrast, the other options include terms that either refer to specific characteristics of stem cells rather than distinct types or mix concepts. Induced pluripotent stem cells (also mentioned in one of the choices) are a type of stem cell that has been engineered from adult cells to become pluripotent, but they are not considered one of the two main categories. Similarly, totipotent and pluripotent refer to stages of differentiation rather than types of stem cells. Hence, the categorization based on embryonic and adult stem cells remains the most widely recognized and fundamental distinction in the field.