Why Do Scientists Pursue Several Methods to Get Stem Cells

Why do scientists pursue several methods to get stem cells to grow into specific tissue types?

A) Science is not a collaborative work,so individuals must develop their own method of growing tissue types.
B) Each method or approach used in stem cell research adds to our knowledge of how stem cells work.
C) The more scientists are involved in stem cell research,the less people will think any research on embryos is unethical.
D) More research on stem cells will be less expensive,over the long term.
E) Scientists are trying to maximize their profit margin.