Adividing eukaryotic cell is treated with a drug that inhibits shortening of spindle microtubules. this will cause the cell division cycle to stop at the stage.

Answer is anaphase

When a dividing eukaryotic cell is treated with a mitotic inhibitor drug, the drug disrupts microtubules. Microtubules are the structures that pull the chromosomes apart when a cell divides. The drug inhibits shortening of spindle microtubules during anaphase stage of mitosis. As a result cell division stops at anaphase stage. Mitotic inhibitors are used in cancer treatment preventing cell from division.

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