Final answer:
The positive cell-cycle regulators that can cause cancer when mutated are known as oncogenes, which are mutated forms of proto-oncogenes.
Step-by-step explanation:
The correct answer to what are positive cell-cycle regulators that can cause cancer when mutated is d) Oncogenes. Proto-oncogenes are the normal genes that, when mutated, can become oncogenes. This mutation can lead to abnormal cell growth and cancer because oncogenes have the potential to alter transcriptional activity, stability, or protein translation of genes that control cell proliferation. An example of an oncogene involved in some cancers is the myc protein, which, when overexpressed, leads to uncontrollable growth of B cells, characteristic of Burkett's Lymphoma.