One difference between cancer cells and normal cells is that
cancer cells
\begin{equation}\begin{array}{l}{\text { (A) are unable to synthesize DNA. }} \\ {\text { (B) are arrested at the S phase of the cell cycle. }} \\ {\text { (C) continue to divide even when they are tightly packed }} \\ {\text { together. }} \\ {\text { (D) cannot function properly because they are affected }} \\ {\text { by density-dependent inhibition. }}\end{array}\end{equation}