Final answer:
New drugs that decrease DNA methylation and prevent the removal of acetyl groups from histone proteins can suppress tumor cell proliferation by inhibiting epigenetic modifications that silence genes in cancer cells.
Step-by-step explanation:
New drugs that decrease DNA methylation and prevent the removal of acetyl groups from histone proteins can affect gene expression in tumor cells and help kill them. DNA methylation and histone deacetylation are epigenetic modifications commonly found in cancer cells, which silence genes and contribute to tumor growth. By inhibiting these modifications, the drugs can prevent gene silencing, leading to the reactivation of silenced tumor-suppressor genes and potentially suppressing tumor cell proliferation. Therefore, the correct answer is d) They suppress tumor cell proliferation.