I am leaning more towards answer A but cannot find an explanation:

Alright! Let's create iPS from Amy's skin cells- iF'S can be developed by altering the gene expression in somatic cells (in this case skin cells} using an adequate set of transcription factors. Every cell in our body uses its own set of transcription factors to regulate gene expression. We need to determine which set of transcription factors to use. Which one would you use? a) Use unique transcription factors that can only be found in stem cells b) Use general transcription factors that can be found in every cell