Final answer:
Unipotent stem cells do not cause teratoma formation, but they may have limited potential for tissue regeneration compared to pluripotent stem cells.
Step-by-step explanation:
Pluripotent stem cells have the potential to differentiate into any type of human tissue, while unipotent stem cells are fully specialized and can only reproduce to generate more of their own specific cell type. Teratoma formation is a concern when using pluripotent stem cells, as they can develop into tumors comprising various tissue types. In contrast, unipotent stem cells do not cause teratoma formation because they are already specialized.
Therefore, option a is correct: unipotent stem cells do not cause teratoma formation. However, it is important to note that unipotent stem cells may have limited potential for tissue regeneration compared to pluripotent stem cells, which have the ability to differentiate into a wider range of cell types.
Thus, option c is incorrect: unipotent stem cells are not considered a safer approach for tissue regeneration compared to pluripotent stem cells.
Option b is incorrect as it states that both pluripotent and unipotent stem cells lead to teratoma formation, which is not true. And option d is irrelevant as teratoma formation is not dependent on the injection site.