Final answer:
d. Specifically inhibits the cell division cycle in rapidly dividing cells.
The most important characteristic for a chemotherapeutic drug to treat cancer is that it specifically targets and inhibits the cell division cycle in rapidly dividing cancer cells to reduce side effects and improve effectiveness.
Step-by-step explanation:
The characteristic that would be most important for a chemotherapeutic drug designed to treat cancer cells is d. Specifically inhibits the cell division cycle in rapidly dividing cells. This is because chemotherapy targets rapidly dividing cancer cells but also affects normal cells with high turnover rates. Finding an agent that specifically targets the replication or mitosis of cancer cells without harming healthy cells is the key to reducing side effects and increasing treatment efficacy. For example, Taxol blocks spindle fiber microtubules from depolymerizing, which hinders mitotic anaphase and telophase, demonstrating a specific interference in the cell division cycle. Therefore, a drug designed to selectively inhibit the cell division of cancer cells, with minimal impact on healthy cells, would be optimum.