According to the scientific article, 'cancer as an evolutionary and ecological process' (merlo, et al, 2006) -why might the concept of evolution by natural selection be useful in understanding the biology of cancer? select two of the following answers

a. a cancer is too intractible and difficult to understand witness the lack of progress in 100 years of fighting it.
b. cancer therapies select for cancer stem cells with resistance mutations.
c. there is evidence for competition, predation, parasitism, and mutualism between co-evolving clones in and around a cancer neoplasm.
d. cancer is always an example of viral predation on higher eukaryotes.