Amedical student divides a cadavers thorax into halves by cutting along the sagittal plane. this cut will divide the thorax into

A sagittal plane is an anatomical plane which divides the body into right and left halves. The thorax would be divided  in left and right sections.

a polymer is a chainlike molecule made up of small molecular units. these small molecular units are called monomers. monomers of polymer can be joined together either naturally or synthetically.  

during the process of dna replication, brdu can replace thymidine and incorporate into the newly synthesized dna, cell proliferation thus can be reflected in the extent of brdu incorporation.