8. Outline the process of metaphase, inclusive of the role of microtubules and the centromere.

Chromosomes are positioned in the middle of the cell during metaphase.  

Explanation:

During metaphase, the centrosomes are at opposite poles or sides of the cell.  The spindle apparatus is formed and the nuclear membrane has dissolved.  The spindle fibers, also known as microtubules have lined up the chromosomes along the equatorial plate in the middle of the cell so each sister chromatid faces opposite directions.  The sister chromatids are still connected by the centromere, and this is the last time they are connected during this division.  The centromere is also where kinetochores assemble, and kinetochores are the sites of attachment for microtubules to pull the sister chromatids apart.  They are important for the cell to be able to divide.  

b. lithosphere, asthenosphere, mesosphere   is the answer most likely