The correct answer is a cancer cells.
Cancer cells often ignore the normal signals that regulate cell growth and division. Instead, they can grow uncontrollably due to mutations and changes in their regulatory mechanisms.
G0 cells are in a quiescent state and do not actively respond to growth signals but can be prompted to re-enter the cell cycle. Immortal cells refer to cells that can divide indefinitely, often due to mechanisms like telomerase activity, but they can still be influenced by some growth signals. Stem cells, on the other hand, actively respond to signals for growth and differentiation.
So, while cancer cells have disregarded normal regulatory signals, the other options (b G0 cells, c immortal cells, d stem cells) can respond to growth signals under certain conditions.