The cell cycle can be arrested in mitosis when a single sister-chromatid pair is mono-oriented on the mitotic spindle. If at this point a glass microneedle is used to pull the mono-oriented chromosome toward the pole to which it is not attached, the cell proceeds to anaphase. This observation confirms that …

A) mono-oriented chromosomes are stable.
B) mechanical tension drives the formation of bi-oriented chromosomes.
C) bi-oriented chromosomes activate the spindle assembly checkpoint.
D) lack of mechanical tension at the kinetochore in at least one chromosome prevents entry into anaphase.
E) mechanical tension at the kinetochore in at least one chromosome is required for entry into anaphase.