You Isolate Cells from a Tumor and Study Them

You isolate cells from a tumor and study them.You observe that the cells continue dividing,even when DNA is damaged,when the cells become crowded,or even when nutrients run low.These observations lead you to suspect that the cells

A) contain a proto-oncogene.
B) contain an oncogene.
C) contain a mutated tumor-suppressor gene.
D) are infected by a virus.
E) are breast-cancer cells.