Final answer:
Microtubules are responsible for moving chromatids during cell division by attaching to the kinetochores and pulling chromatids toward opposite poles as they shorten.
Step-by-step explanation:
The correct answer is A) Microtubules. During cell division, specifically mitosis, microtubules that make up the mitotic spindle are responsible for manipulating and ensuring the proper separation of sister chromatids into the two new daughter cells. These microtubules become attached to the chromatids via protein structures called kinetochores, which are located at the centromeric region of each chromatid. As microtubules shorten, they pull the attached chromatids towards the opposite poles of the cell.