why might the researchers have used both mahlavu and focus cell lines in their ic50 experiments, considering that both are liver cell lines? a. one cell line is from a healthy liver, while the other is from cancerous liver cells. b. different cancers may exist within the same tissue and may respond in different ways to possible therapies. c. one cell line came from a human, while the other came from a mouse. d. it was unnecessary; the scientists could have selected only one of the cell lines for use.