A scientist is testing new chemicals designed to stop the cell cycle at various stages of mitosis. Upon applying one of the chemicals, she notices that all of the cells appear as shown below. Which of the following best explains how the chemical is likely acting on the cells?

(A) The chemical has arrested the cells in prophase and has prevented attachment of the spindle fibers to the kinetochore.
(B) The chemical has arrested the cells in metaphase and has prevented dissociation of the spindle fibers from the centromere.
(C) The chemical has arrested the cells in metaphase and is preventing the shortening of the spindle fibers.
(D) The chemical has arrested the cells in anaphase and is preventing the formation of a cleavage furrow.