Which is a controversial ethical issue
manufacturing synthetic limbs
using embryonic stem cells
transplanting synthetic organs
using drone aircraft in war zones

using embryonic stem cells

Explanation:

Researchers current are focused on the therapeutic effects of the use of embryonic stem cells, that may be used for the treatment of diabetes and heart diseases.

However, there is an ethical debate, which centers around the fact that it is necessary to destroy embryos to use these cells.

So the correct answer is:

using embryonic stem cells

answer; (religion)

answer; /// i believe the correct answer is (oasis)