Question

Tissue engineering and stem cells:

are only useful for immune deficits

are experimental therapies not yet in use

are widely used for a variety of conditions

have not been proven to work

are only useful for certain anemias

Answer 1

are widely used for a variety of conditions

Reason: several stem‑cell and tissue‑engineering therapies are already in clinical use (e.g., hematopoietic stem cell transplants for blood/immune diseases, engineered skin grafts, corneal limbal stem‑cell transplants, some cartilage/soft‑tissue products), and many more are in active clinical development.