Answer:
The correct answer is it involves killing human embryo.
Step-by-step explanation:
Stem cells are the pluripotent cells which have the ability to differentiate into any type of cells throughout their lifetime but research on stem cells has become a topic of ethical, social and moral issues as the stem cells are formed just after the fertilization which means they are found in the embryo and so is called Embryonic stem cell (ESC).
Therefore, in order to get embryonic stem cells, the embryo has to be destroyed and killed which is against the value of human life.
Thus, it involves killing human embryo is the correct answer.