A friend declares that chromosomes are held at the metaphase plate by microtubules that push on each chromosome from opposite sides. Which of the following observations does not support your belief that the microtubules are pulling on the chromosomes?
选项：

A:the jiggling movement of chromosomes at the metaphase plate
B:the way in which chromosomes behave when the attachment between sister chromatids is severed
C:the way in which chromosomes behave when the attachment to one kinetochore is severed
D:the shape of chromosomes as they move toward the spindle poles at anaphase